ONLY do this if all else fails. A normal FORMAT should work in 90% of the cases (when several virus scanners don't work), but if it's really nesscary, the steps to FDISK and FORMAT your drive are below...
Note: I haven't installed a Win98 machine in a while, so I might be missing a step or two (though I think I have it all)...
0) Back up all data you want to have saved!
1) Get a bootdisk with both FDISK and FORMAT on it.
2) Reboot to the bootdisk
3) Run FDISK
4) Select which HD you want to mess with (can't remember what menu you need to go into)
5) Delete the primary partition on your drive (if it's a really nasty virus and you have multiple partitions, you might delete those too)
6) Re-Create your partition structure how you want it. This is a pretty confusing step, so take your time
Usually takes me 2 or 3 tries to get all my partitions right (unless you only want one big partition).
7) Exit FDISK
8) Type in FORMAT C: /s (this will format your C partition you created, as well as make it bootable)
9) Stick in your Win98 CD and reboot
10) Point windows to where you want it to install, and let it rip
JigPu