Basically, you could even leave it there and install another OS on your drive D. On my machine that's what I did - I originally bought the computer with Vista installed. Then 7 came out and I wanted to try it, so I got another hard drive and installed 7 on it, doing nothing to Vista. Now I have a dual boot machine. Moreover, each OS sees the drive on which it is installed as drive C
- there is no reason for two different OS to keep the same letter assigned to the same drives.
Of course, I understand that you want to change the drive you are having problems with. I just wanted to illustrate what was already suggested before - you can simply install an OS on another drive, and do whatever you want with the faulty drive - leave it, pull it, replace it.