It's time to reinstall Windows, what should I backup in iTunes?

I am getting ready to wipe my hard drive and reinstall Windows. The old computer has gotten too slow and running malware checkers and CCleaner don't help any more. So I decided to just bite the bullet, erase the drive and start over with a clean install of Windows XP.

I know that I need to unregister the computer through iTunes before I do this, but what else do I need to back up to reduce the amount of time it takes to get iTunes reinstalled and back up and running. I have already backed up all of my MP3's to an external hard drive. I looked for some type of FAQ for this process but have not had much luck.