Windows was unable to complete the format

After being messed up with malware which has also caused my registry to get messed up I started working on a newer more powerful machine. Now I am trying to set the old machine (a Dell Pentium 4) up for remote entry to the PowerSpec. So I wanted to scrub the hard drive and begin again. When I right click on the "C" drive from 'My Computer' it gives me a format option. Clicking that I see the message 'Windows was unable to complete the format' which I initially thought to be tied into my start up, but it keeps moving and if I go far enough, the desktop disappears and the machine reboots. Any ideas?