|Boot up with a 95/98 bootdisk and at the a:\> prompt type format c: and enter, where C: is the drive you want formatted. If you wish to format a different drive, substitute that drive letter instead of C:|
Of course, you mention both 95 and 98. You can't format a fat32 drive with the older 95 as it doesn't support it.
And you'll have nothing left on the drive you format so you probably will need an OS cd and do a fresh install.
And some cd's are bootable, in which case you can boot with one of those instead of a bootdisk, if your old PC has the option to boot from the cd.
More background might be helpful.
You're not really green until you're soylent green.