It is much easier to set up a system to be dual-boot if Windows 95/98 is installed first, but it certainly is possible to set up dual-boot on a system that is already installed with Windows NT.

First, keep the following point in mind:

1. Windows 95/98 cannot be installed on any drives that are formatted as NTFS, nor can it currently view any data on such drives.

Therefore, if you want to run dual-boot and have either operating system see all the drives on the system, you must keep them formatted as pure FAT (also called FAT16).

The information below is primarily from Microsoft's Knowledge base.

Steps for setting up dual-boot on a Windows NT system:

1. Start the computer from an MS-DOS floppy disk (a Windows 95/98-startup diskette should work fine). The diskette must contain the sys.com file. Transfer that file to the boot drive by executing the following command: sys a: c:
   The message "System transferred" should be returned.
2. Remove the diskette and reboot the system. It should boot to an MS-DOS command prompt. Install Windows 95/98, as it would normally be done, making sure you do not delete the partition that Windows NT is installed on.
3. After all installation reboots of Windows 95/98 are complete, boot the system using the Windows NT Setup diskettes. Setup will start, and display a menu of options. Select "R" to Repair Windows NT. Instruct the repair process to ONLY repair the Windows NT boot sector, do NOT choose to inspect the registry or system files, or the Windows NT boot environment!
4. Reboot and the system should start Windows NT as normal. Now, edit the boot.ini file found in the root directory of the boot drive, and add the following line under the Operating System section: c:\="Microsoft Windows"

Once completed, upon booting the system you'll see a menu that has three entries similar to this:

Select the options you want and press enter. "Microsoft Windows" will boot your previously installed Windows 9x.

To change which option is booted by default, boots into Windows NT, right-click on My Computer and select Properties. One of the tabs is "Startup/Shutdown". From that tab you can select which item is booted by default, and how long the default countdown time is set at.