You want to do a dual-boot install of W98 and NT. Let's assume that your machine boots from the CD. The process is going to be pretty straightforward.
Boot to the W98 CD and wipe all partitions.
Boot again to the CD and partition the disk into two partitions. Give the partitions enough space to hold the OS (200MB for W98 and 400MB for NT) plus applications and so for
Boot again to the W98 CD and install W98 into the first (C:) partition. Use FAT for a partition format, because NT doesn?t understand FAT32.
Now boot to the NT CD and point Setup at the second partition. Don't install two Windows operating systems into the same partition, even if you put them in separate system folder. The common files in Program Files are not binary compatible.
When you do the NT installation, Setup will copy the boot sector to a file called BOOTSECT.DAT and save it to the root of the C: drive.
When you boot to NT, you'll get a boot menu that includes the alternative Windows operating system. Select this and the machine will boot into W98.
This was first published in May 2001