How to format my compuer

Er, you shouldn't do that. But, nevertheless, go to My Computer from your desktop, right click said drive and click format. Follow the prompts for options and you'll probably get a warning message. You should read it and think about it. :P Cheers.

Yeah, after it's formatted, it won't be usable. This is a bad idea.

Why are you trying to format you drive?

Is this another drive on your PC or are you trying to reinstall windows?

How to Format Drive and Install Windows from Scratch
Geek to Live: How to format your hard drive and install Windows XP from scratch