Swap the drive to the primary IDE channel (other socket on the motherboard) and set all drives to Auto in the BIOS.
The drive will now be the C drive
Set Bios to Boot a, CDrom, C.
reboot the PC it will look for an op system first from the floppy then the CD and finally the hard drive. This will allow you to boot from a floppy to set CD drivers (as per windows98 install), or boot from a bootable CD (as per Xp install).