are you saying fdisk cannot format the drive?
maybe its kaputt!
if you are saying there is still an OS on the drive but you cant boot from it try downloading the win98 oem boot disk click here (will even work with xp)
copy it to a floppy disk
make the floppy drive the first boot device in the bios
put the floppy in the drive and turn on the computer
wait for it to load and then type
this will restore the master boot record
remove the floppy and press ctrl+alt+del to restart.hopefully it should boot.