Depends on your O/S. Win2k and XP, stick the CD in, boot from it and follow the installer through. It should prompt you to either format or delete the partition.
Win98/SE/ME, you need a bootable floppy disk. Try <A HREF="http://www.bootdisk.com" target="_new">here</A>. Boot from it, and type <b>format c:/s</b>
<font color=blue>"We didn't underestimate them. They were just a lot better than we thought." - Bobby Robson</font color=blue>