Just need to add some info that will affect most users, when doing a Repair Install afterward you may loose the ability to sign on to MSN Messenger, to solve this problem have a look at this thread
Unable to sign in to WLM
Another thing you might find is you loose your custom themes and this is due to not having permisions set on the old themes, go to the themes folder in
C:/Users/Your User Name/AppData/Local/Microsoft/Windows/Themes and use the Take Ownership shortcut in your context menu found here
Take Ownership Shortcut on the themes folder and you will now have all your themes back.