PC: Harddrive & XP formatting issue

Well in my computer junk room, I found a 40 gig harddrive I didn’t actually know I had… Anyways, I decided to pop it into this box. Windows has been yelling at me that it’s partition is too small, so I decided to:

  1. Format and partition the new drive into two drives, one for windows and one for other stuff.
  2. Install windows on the new drive
  3. Reformat my entire old drive, wiping everything.

Well I’ve got windows reinstalled on the new harddrive, and that’s the windows I’m running. But stupid freaking xp wont let me wipe the c:\ partition on the old drive, because it claims I’m using it.

Ok, so I got angry at it, and did something dumb: I deleted everything on c:. Well that wasn’t that dumb, because everything still seems to work. But stupid freaking xp STILL wont let me format c!

Any ideas on how I can format c?

Here is a picture of my drive setup (windows is on H:):