I would probably recommend the Home Edition for you. It's cheaper, and I think it has all you would need.
And the best thing to do is back up all necessary files and install XP clean (that is, wipe the drive clean before installing). Make sure you backup your music, movies, saved games, documents, favorites and any other file you couldn't easily recreate. By that, I mean don't back up your applications because you can easily reinstall them.
Do you have a CD burner? That'll be your best bet with backing up.