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Install any Windows 9x on Windows NT (FAT)

Last reviewed: March 2004

Dual-Boot Windows Me, SE, 98, 95b/c on a Windows NT (FAT) system.

You can install any Win9x on a FAT system that has Windows NT already installed on it. You can then select either Windows during boot up. No third-party boot utility is used here.

C: must be the PC system partition. C: must use FAT because both OSs use C: during the initial boot process. NT can't read FAT32, and Win9x can't read NTFS.

If C: uses NTFS then you must read Any 9x on NTFS (XP/2K/NT).

You have two options:
#1 Repair
You can install Win9x on a different FAT partition. Then repair the NT boot sector with its CD or Setup Disks (no data loss).
#2 Reinstall
Fdisk, repartition, format, and install the Win9x first. Then reinstall Win NT (data loss occurs but you can first create an image of NT and restore it later).

Please read Dual-Boot Win9x/XP/2K/NT (read first) for an overview of Windows dual-booting.

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You can use #1 Repair or #2 Reinstall methods, or use a utility.

Win NT will have control of the boot up and allow booting to Win9X or NT on boot up.

If C: is an NTFS partition, you must convert C: to FAT with loss of data and use the #2 Reinstall method, or else use a utility.

#1 Repair:
Installing Win9x on a Win NT system often makes NT unbootable. In this situation the NT boot sector can be overwritten by the Win9x boot sector. The NT is still intact, but can not boot! Fortunately its boot sector can be repaired and a dual-boot created. Win 95 will definitely behave in this manner. Some installations of Win 98 on an existing NT system create an immediate dual-boot and the repair is not necessary.

Install the Win9x, optionally save the Win9x boot sector, and then repair the Win NT boot sector. This requires extra user participation, but no data lost occurs. It needs C: to be FAT, not NTFS. FAT32 must not be used. If there's only one partition then add a hard disk or use partition utility.

#2 Reinstall:
Installing Win NT on a Win9x system does not affect the Win9x's ability to boot. Win NT detects the presence of the existing OS (Win9x) during the NT installation and makes the appropriate adjustments. NT are designed to cope with this situation and create dual-boot boot up options.

Start from new. Fdisk, repartition, and format C: as a FAT partition. Install Win9x as the first OS (on C:), and then reinstall Win NT elsewhere as NTFS or FAT. This option is more reliable, but all data is loss and it takes more time.

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One possible difficulty is that you need at least two partitions (or hard disks).

Win NT and a Win9x should not be installed on the same partition. Installing different Windows on a single partition may cause problems running those OSs. At a minimum the items in Program Files, including those Common/Shared components, will cause conflicts. IE and Outlook Express are likely to break, and other applications are also at risk. A single hard disk is fine, but it should be partitioned to at least C: and D:

The OS boot partition for Win9x or DOS must be a Primary partition. Win9x's files can be installed on any other Logical partition provided it use FAT. However, remember the caution that the C: drive must never be, or altered to, NTFS. The Win9x partition must be formatted prior to the Win9x installation.
NT can be installed on a Primary or Logical partition. Also, NT can handle multiple Primary partitions on one hard disk, but that can cause problems for Win9x and is best avoided.

If you have a single hard disk with a single partition (a C: drive, but no D: except for a CD or DVD drive), then it's recommended that you Fdisk, repartition, & format C: to a FAT/32 (with total loss of data!). A third partition is useful for shared data if readable by both Windows. If you must repartition (and reinstall the Windows) then do it! You can use this opportunity to take a long-term view of your partitioning needs.

Click HERE to learn how to install another hard disk without changing current drive letters.

A third-party partition utility will allow you create/resize partition(s) without loss of data.
PartitionMagic 5.01 was FREE with PC Magazine CD, June 2002 (PM is now ver. 8).
PartitionMagic 4.0 appears to be FREE at (not verified).
Some users may find a freeware utility like Partition Manager (165KB) difficult to use.

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It's worthwhile emphasizing the importance of FAT types with a Win9x.

Windows 9x can not boot from an NTFS partition. Windows NT can not boot from FAT32.

There are four important ingredients to a Win9x installation:
1. PC system partition type (C: must always use FAT or FAT32)
2. Win9x boot files (always on C:)
3. Win9x boot partition (usually C: but can be elsewhere using same FAT type as C:).
4. Win9x boot partition must begin before 2 GB (Win95,a) or 8 GB from physical start of disk
    - 98+ can boot from beyond the 8 GB boundary if the system supports INT13 Extensions.

Therefore, in this dual-boot:

• If NT is installed on C: and uses FAT, then you just need a second FAT partition (for Win9x).
• If NT is not on C: and uses FAT elsewhere, then install Win9x on C:.
• If NT is not on C: and uses NTFS elsewhere, then C: can be FAT.

• If NT is installed on C: and uses NTFS, then use #2 Reinstall, or use a boot utility.

• If you have only one partition then you must:
     start fresh using the #2 Reinstall method (data is lost when you repartition),
     or add a second hard disk (no loss of data),
     or use third-party partition utility to create more partitions (no loss of data).

Adding a disk will alter drive letter allocations if current disk has more than one partition!

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EXAMPLES: Install Any Win 9x on Win NT (FAT)

Examples of Partitions & File System types that can be used in this Dual-Boot.
A second hard disk (Disk 1) is helpful, but it is partitions and file system types that count most.

Example 1:
Disk 0  C:  Win9x  FAT  Primary (PC system partition;  2GB max.) 
Disk 0  D:  NT4.0  FAT  Logical (both Windows can read both drives) 
Example 2:
Disk 0  C:  Win9x  FAT  Primary (PC system partition;  2GB max.) 
Disk 0  D:  NT4.0  NTFS Logical (NT can read both. Win9x can't read D:) 
Example 3:
Disk 0  C:  NT4.0  FAT  Primary (PC system partition;  2GB max.) 
Disk 0  D:  No Win FAT  Logical (data shared by both Wins)
Disk 0  E:  Win9x  FAT  Logical (both Windows can read all drives) 
Example 4:
Disk 0  C:  No Win FAT  Primary (PC system partition;  2GB max.) 
Disk 0  E:  NT4.0  NTFS Logical (NT can read all drives) 
Disk 1  D:  Win9x  FAT  Primary (Win9x can read only C: & D:) 
Disk 1  F:  No Win NTFS Logical (NT data) 

When C: is not the OS Boot Partition:
The OS boot partition must begin before a certain distance from the start of the hard disk to be bootable. The OS boot partition for DOS, FAT, NT must begin before 2 GB from the start of the hard disk. The boot partition for other Windows must begin before 8 GB from start of disk. If your PC supports INT13 Extensions, then 98+, XP, 2000 can boot from beyond 7.8 GB.

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Remember, you will need to repartition or add a hard disk:
  • if you have only one partition (only a C: drive).
Remember, you will need to format your C: drive:
  • if that PC system partition is not a FAT or FAT32 partition.
Note: PartitionMagic 5.0 was freeware with PC Magazine in June 2002. Get a copy!

OEM Windows 95B & 95C (OSR 2.x) starting errors with some 'fast' processors.
If you wish to install OEM Win95B or OEM Win95C on a system with one of the following processors, then you must read this first for a recognized software fix that is required.
  • AMD K6-2 (350MHz or faster)   • Pentium III (1GHz, or faster)   • Pentium 4 (any)
This does not apply to Win98, 98SE, or Me which come already fixed.
The fix does not correct the problem for the retail version of Windows 95.

Win95 OSR2 Bug.
Some Win95 OSR2 versions cause the system to hang when you select the Boot Previous Operating System option during Win95 startup (pressing F4). This can be corrected using the SYS C: command followed by fixing the NT boot sector.

Uninstalling Win 9x.
Never 'Uninstall' Win Me from a dual-boot. You should edit Win Me out of Boot.ini, and manually delete all Me's folders and files. Win Me's Uninstall.exe restores a backup copy of the Me partition information (stored in c:\Suhdlog.dat) even if the partition information has changed.
Uninstalling Win 98 Upgraded from Win95 in a Dual-Boot. Uninstalling the Win98 upgrade may delete boot.ini. Recreate it. Also, the uninstall deletes the Bootsect.dos file (save it first).
"Do you wish to enable large disk support (Y/N)?"
When Fdisk asks you this, it wants to know if you wish to use the FAT32 file system.

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Prepare to Install Win9x & then REPAIR the Win NT boot sector (no loss of data expected).
Already Installed: NT . You want to add : WinMe, or 98/SE, or 95.


1. Hardware drivers compatible with next Windows (mainboard, hard disk, video, ..)
    For those in Windows, check list shown in \Drivers\ on its CD.
2. Check that C: uses FAT (it must be the only Primary partition).
    Check that you have at least two partitions (or two hard disks).
    You need another FAT partition (for Win9x) if NT is installed on C: and uses FAT.
    You need to use the #2 Reinstall method if C: uses NTFS.
3. Read, & save, the Repair a Dual-Boot page.
4. Get a boot disk/Startup Disk, with CD support, for a Win9x or DOS 5+ - ESSENTIAL.
5. Download (6 KB) from THPC (you must read about Bootsect.DOS).
    Extract all three files (17.5 KB) from to the Win9x boot disk
    Boot disk must contain the MS-DOS files Debug, Choice, Attrib, Sys (same ver).
6. Create NT's ERD (run Rdisk.exe /s), and boot disks - ESSENTIAL
    WINNT32 and MAKEBT32 (\Boot disk folder on CD) are used to create boot disks.

Update NT with its SP 5(+) to use a large NTFS drive.


Installing Win9x on a Win NT system and then REPAIRING Win NT.

The C: drive must not be an NTFS or FAT32 partition. FAT16 is usually called FAT.

1. At least two partitions - two hard disks will also do fine.
2. C: must be a FAT partition. C: must not exceed 2 GB in size.
3. A FAT partition not used by NT (you may need to use PartitionMagic).
4. Win NT installed and updated with the latest NT SP.
5. Win NT CD and/or Setup floppies, & ERD (Rdisk.exe /s) - ESSENTIAL.

6. Boot disk / Startup Disk for a Win9x or DOS 5+ (with CD support) - ESSENTIAL.
7. downloaded from THPC, and unzipped to that Win9x boot disk.
8. A full Win9x Installation CD, or copy the installation files to a FAT partition.

9. Read, and save, the Repair a Dual-Boot page BEFORE you start.
10. Read the Bootsect.DOS page.

Note: In an emergency any Win9x Startup Disk (with CD support) can be used for running a NT CD. Boot up with it and run WINNT.EXE from the I386 folder of your NT CD.

Note: contains Btsect.bat (and Bootread.scr) which is used to copy an image of the Win9x boot sector in C:\Bootsect.DOS. The ONLY time a valid Bootsect.DOS can be created is when C: is a Win9x boot sector. It's sensible to image the Win9x boot sector while it exists, and before the XP/2K repair replaces it with its own sector. Let's avoid any possibility of later receiving a "Bootsect.dos is missing ..."!


Install Win9x & then REPAIR the Win NT boot sector (no loss of data expected).
Already Installed: NT . You want to add : WinMe, or 98/SE, or 95.

Repair Procedure:

1. Prepare (above), and switch OFF anti-viral software (& check in BIOS/CMOS also).
2. Boot up to true DOS with DOS/Win9x boot disk. At the A: prompt type
     x:\Win98\Setup.exe /is for Win 98,
      or x:\Win95\Setup.exe /is for Win 95,
      or x:\Win9x\Setup.exe /is for Win Me where x: is your CD-ROM drive.
      Select Other directory to install it on the FAT partition of your choice.
      Fully install Win9x on a FAT partition not used by NT:
3. Install all required drivers and ensure the installation is satisfactory. Do this now!
4. Boot up the prepared Win9x boot disk to true DOS and
      run A:\Btsect.bat (this creates Bootsect.DOS).
5. Create a new Startup Disk for the new Win9x (must contain
6. Boot up with the Win NT Setup/Install boot disks, or the NT CD.
      Select R to repair installation, and execute a repair of the boot sector.
      Use your repair disk if your NT installation can't be found. Reboot.

When your computer restarts, the Windows NT boot loader screen appears, and you can choose between "Microsoft Windows 9x" and Win NT. If not, read Repair a Dual-Boot.

7. Finally, always create a new Rescue Boot Disk when a new dual-boot is successful!

Note: If rebooting for hardware installation, be sure you select the correct OS!

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Prepare to Install Win9x and then REINSTALLING Win NT
All hard disk data will be lost.
1. Hardware drivers compatible with next Windows (mainboard, hard disk, video, ..)
    For those in Windows, check list shown in Drivers on its CD.
2. Backup important data/settings/passwords/e-mails/etc.
    Optional: Save an image of NT (for restoration later).
3. Boot up with a boot disk for a Win9x (with CD support).
4. A:\Fdisk & repartition the hard disk. Create two(+) partitions.
    If faced with NTFS on C: then use A:\FDISK /MBR from Win9x boot disk,
    or use NT Setup disks and remove the NTFS partition (exit without installing).
    DO NOT Enable large disk support (that creates FAT32).
    Make C: the only Primary partition on that hard disk, and mark it as Active
    Format C: and any other Win9x partition(s) using FAT16 ("FAT").

1. DOS or Win9x boot disk that supports your CD drive and has Fdisk & Format.
2. At least two partitions. C: must be the system, only Primary partition, and use FAT.
3. A full Win9x Installation CD - obviously!
4. Win NT Installation CD - obviously!
5. Floppy - for a new Win9x Startup Disk (that contains SYS.COM) - ESSENTIAL.
6. Floppies - for Win NT Setup disk set, and ERD - ESSENTIAL.
7. Backup of important data, settings, passwords, e-mails, everything you need!
8. Optional image of NT (for restoration, later, on same directory & partition).
9. Read and download THPC's Repair a Dual-Boot page BEFORE you start.
You are not restricted to just two OSs if reinstalling.
Multiple OSs can be installed, but install the oldest OS first while you have the choice to do so.


Fdisk. Install Win9x & then REINSTALL Win NT on different logical partition.
This is simple, safe, and reliable. Its also time-consuming, and data loss will occur.
If you want to use MS-DOS (FAT), install it FIRST, then Win9x, finally Win NT.

Reinstall Procedure:

1. Install Win9x on C:, or on another FAT partition.
2. Create a new Win9x Startup Disk (that contains SYS.COM) - ESSENTIAL.
3. Reboot. Install all required drivers, and ensure a good installation. Do this now!
4. Boot up to Win9x and install Win NT on a different partition - use Advanced.
      Make sure it installs as a new installation - not as an upgrade.
      Make sure the installation drive letter is not the Win9x drive.
      Make sure the directory name is not the Win9x name.
      Let NT format its partition and select FAT for the target drive,
      or select NTFS (and lose access to all NTFS data when in Win9x).
      Do not alter the FAT type of C:.
5. Create the Setup floppies, & ERD (Rdisk.exe /s from NT prompt) - ESSENTIAL.

On restart, the Windows NT boot loader screen appears, and you can choose between "Microsoft Windows 9x" and Win NT. If not, read Repair a Dual-Boot.

6. Finally, always create a new Rescue Boot Disk when a new dual-boot is successful!.

Update NT with its SP 5(+) to use a large NTFS drive.

Note: If rebooting for hardware installation, be sure you select the correct OS!


To start MS-DOS from a Windows 9x multi-boot with Windows NT:

This, obviously, applies only if MS-DOS was installed before Win9x.
Remember that Win Me does not allow booting to a 'Previous version of MS-DOS' !

1   Choose MS-DOS from the menu on boot loader screen, and press ENTER.
2a To start MS-DOS directly: press F4 just as Win9x starts to load.
2b To display Windows 9x Startup menu, press F8 instead
     and, then to start MS-DOS, choose the Previous version of MS-DOS option.

But check this first:
For the MS-DOS option, the line
should be in the [Options] section of the Win9x Msdos.sys file.

To add BootMulti=1 to Msdos.sys:
Open a MS-DOS Prompt, and type in (assuming C: is the PC system partition)
  Now add the line
  to the [Options] section.
  Save, and Exit.
Finish by typing in (and then press Enter)

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Specifying the Default OS to Boot, and the Boot Menu delay (the Timeout)

When you have established Dual-Booting, you will want to set which OS boots by default.

You can set the default OS (and the timeout) that you want via Control Panel.

1. Boot to the Win NT.

2. Go to Start > Control Panel > System > Advanced tab (or Properties)

3. Under Startup and Recovery, click Settings (or look for these settings).

4. Under System startup, in the Default operating system list, click the OS that you want to start when you turn on, or restart, your computer.

5. Also select the Display list of operating systems for check box, and then type the number of seconds for which you want the list displayed before the default OS starts automatically.

You can also edit the boot options file (click Edit). Be careful of typing errors if modifying the boot options file (Boot.ini) manually, because doing so may make your computer unusable.

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NEVER dual-boot without your personal safety net - a BOOT DISK for XP/2K/NT.
If stuck, use a Win9x Startup Disk (CD support), and run WINNT.EXE from I386 folder on CD.

RESCUE BOOT DISK for when XP, 2K, NT will not boot - ESSENTIAL, 1 floppy
   Create a bootable floppy to get XP/2K/NT running even if the boot record,
   or boot files, are ever a problem. Write-protect and keep it safe.
      Format a floppy with that XP, 2K, or NT. It must be a full XP/2K/NT format.
      Alter file Attributes (Attrib -r -s -h) of these files in root of C: (PC system partition)
      Boot.ini, NTLDR,, and Bootsect.dos & Ntbootdd.sys (if present)
      (plus Arcldr.exe & Arcsetup.exe - for Windows 2K) and copy them to the floppy.
      Write-protect the floppy. Then restore original Attributes to the files on C:.
      Read the Rescue Boot Disk page for fuller details, plus a much improved Rescue disk.
Use the CD: If you have a Bootable installation CD you should check if your BIOS
   supports booting from it. This is hugely convenient, but still create the floppy.
ERD XP, 2K, NT: Emergency Repair Disk - repair key Registry entries and partition geometry
2K/NT Setup Boot Disks: (4 floppies for 2K, or 3 for NT)
   Use WINNT32 and MAKEBT32 from 2K/NT (Boot disk folder on CD).
   Use WINNT and MAKEBOOT from a non-2K/NT system (such as Win9x).
XP Setup Boot Disks: (6 floppies)
   Read the Microsoft page How to obtain Windows XP Setup boot disks.
   It provides free downloads that create setup boot floppies for all versions of Windows XP.
   Each download is specific to each XP version (Home/Pro; original/SP1/SP2).
Win9x/Me Startup Disk:
   (95+) From a Windows: Control Panel > Add/Remove Programs > Startup Disk tab.
   (98+) From true MS-DOS: Go to the Command folder in Windows, and type Bootdisk.
   Windows 95 Startup Disks do not have CD support (add your CD-ROM driver).
   You can download free Win9x/Me boot disks from (IDE CDrom Drivers Included).

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Please remember that you alone are responsible for the consequences of any changes you make to your computer hardware or software.

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