Do you have a windows 98 boot floppy? Might be better to boot from the floppy and run [fdisk] to check what partitions are on the drives.
You can make a boot floppy from a working 98 machine from the system menu, right click 'my computer' > properties and the 3rd tab at the top of the window. I think... been a while since I looked at 98.
Use Fdisk to departition and then repartition using the same tool (needs a couple of reboots) then [format C:]
That way you're working from a clean slate on all the machines.