Move back from NTFS to FAT32

I was going to install win2k in this old machine but then I got the NTLDR missing file error, although I found a fix for it I decided to just load win98 in it. The problem is that the hard drive was already converted to NTFS and windows 98 runs in FAT 32. How can I reformat the hard drive so I can install win 98 in it?
Thanks for your support!