Dilkhaz
Open up System Restore, click Choose a restore point and click on the date beofre your friend made that change to your computer. Your computer will be restored to how it was beofre your friend ever touched it. If that doesn't work, open up System restore again, and chose an even earlier point. If worst comes to worst, use the earliest restore point, which will cause your computer to be set back to how it was when you first bought it from the storePersonal experience. I did that too with myspace (I wanted to keep my sisters out of it) but then I forgot the password and I had to use system restore.