i think the win 98 disk will work. Just put the disk in the floppy drive and boot the computer. when you get to the A:\ prompt type: format C:
this will format/erase the hard drive. just make sure you have a ackup of your files/programs, they will be gone when you format the drive.
After taht is complete, just insert the win 98 cd rom and your computer will guide through the process.