Castanet Communications banner image

How to dual boot Windows 9X & NT 4.0
Author: Craig "hachiroku" Mercer
Date Created:2002-05-13
Operating System(s):Windows Logo imageWindows 2000/XP

Step 1 - Delete existing partitions
Step 2 - Make 2, 2GB FAT16 partitions (one for Win98, one for NT)
Step 3 - Install Win98 into the first FAT16 partition (C drive)
Step 4 - Install WinNT into the second FAT16 partition (D drive)
Step 5 - Tweak to tastes!

Don't even think about attemptiong this without all nessecary disks, CD's and drivers or you will be sorry! It's not's when and how bad!

(If your starting from a fresh drive skip to STEP 2)
Make a full back up of all data you wish to keep from the existing OS. Next boot from a floppy or CD and enter FDISK. When you enter FDISK it will ask you whether you wish to enable large disk support. Answering yes will enable FAT32 partitions, where as answering no will enable FAT16.

NOTE: Be sure to enter NO to large disk support to enable FAT16 or none of this will work. The reason is because NT cannot see past a FAT32 partition, so, if you install Win98 into a FAT32 partition you will not be able to install WinNT past the Win98 partition.

(for this step you will need a Win98 boot floppy, or CD)
Boot from Win98 BootFloppy or CD. Enter FDISK and create 2, 2GB FAT16 partitions. Exit from FDISK, reboot the machine. Format the first partition (C drive) using the <format c: /u/s> command (without the <>)

NOTE: You can format the second partition (D drive) now, however WinNT will probably want you to reformat it during the NT install. Just make sure to format it using the FAT16 format option when you are prompted!

(for this step you will need a Win98 boot floppy, a Win98 CD to install from and your Win98 CD KEY)
Install Win98 into the freshly formatted FAT16 C drive either from the CD or as we do it; make a new directory on c: called cabs using the <md> command(without the <>) and then copy the contents of the Win98 directory from the CD to c:cabs on C drive. Then run setup from the c:cabs directory. You can set up Win98 to your hearts content and then proceed to STEP 4.

(for this step you will need a set of NT boot floppies, an NT CD to install from and your NT CD KEY)
Next reboot to a set of 3 NT boot floppies or from the CD. WinNT will run through it's set up and ask you which partition to install WinNT into. Choose D drive, (it may ask you to format D, and if it does make sure to format it using FAT16 not NTFS!) and install NT into the default d/winnt directory.

NOTE: To make a set of boot floppies from an NT CD. You can run the <WINNT.EXE /OX> command from inside the /i386 directory on the WinNT CD.

NOTE: To boot from a CD you may have to enable it in your BIOS. Most BIOSes can be accessed during the boot sequence by hitting the ESC key, for some you need to hit F2 or some combination of other keys. See your documentation or manufacturers website.
Once in the BIOS you can select the boot options for floppy (a drive), cd-rom or hard disk in different orders. Usually the cd-rom is not selected to boot from!

Well that's it! If everything has gone well, you are feeling very proud and ready for a cold one! If you have not succeeded you may want to check the following:

  • Did you do wipe the Hard Drive clean (delete all partitions and make new ones)?
  • Did you format both partitions using FAT16? (If you fortmatted using FAT32 or NTFS it will not work!)
  • Did you install Win98 first?

Once you get it running you can tweak both OSes out to your hearts content. The really awesome thing about having both systems able to see each other (because of the FAT16 partitioning) is, if one is having a problem, you can boot into the other, search the internet, download drivers etc. and make them available to the other operating system!

The biggest piece of advice I can give you is have all your drivers handy and the proper CDs you need BEFORE YOU START! If you do get into trouble, be sure to visit or for help.