If it is a Dell of any sort you should press F12 to get the boot menu up.
If not try to get the boot menu up.
If you have a Xp or Vista or NT WORKSTATION 4.0 setup disc put it in the computer and boot from cd.
XP gives you the option to partion and that can mean a way to format i think vista does. (Mine came preinstalled).
Not sure if NT does.
Anyway let me know how you get on.