You need to use a windows boot floppy to start things off, then at the "A" prompt type "format c:" restart the computer after formatting, partition with "fdisk" if necessary and with your win 98 cd in the drive type "setup" at the "E" prompt or what ever your CD rom drive is.
IMO get windows XP, lot easier to work with.
Just google boot disk if you need to get a win98 boot floppy, tons of sites out there.