Do you have your windows disc? If so then just put it in, reboot and follow the instructions for reinstalling windows. Part of the installation is the option to format the hard drive.

Mut, how familiar are you with DOS?

For example do any of these mean anything to you?

Format c:/s
Fdisk
Primary partition
Active partition

I'm just a bit concerned that if you go down the road of formatting into DOS you can come unstuck easily without the background knowledge.

Don't do it Mutt, please; get someone who knows their stuff to sort it for you. You won't regret it.
Once you start formatting, if you're groping around in the dark the only possible outcome is misery.

Bring it round here I'll do it for you.

Same advice here Mut, thats where I was going with the DOS questions. One you format with a dos disk you are into old fashioned (but much more logical) black screens and typing commands long hand complete with switches.

Dos typically with boot into a D: virtual drive with the core dos tools on it. From there you need to be typing stuff like

Format c:/s
Are you sure Y/N
[ENTER VOLUME]

do you know what the volume is or where to find it?

If the above is not immediately clear to you then leave well alone.

Format with the windows XP disc, its automated. If it didn't work last time then try again, you probably did something wrong.

There goes Mutley offline for another 2 months!