15. Re-install Windows
This is the scorched earth policy -- but it's not as drastic as you might think. Many PCs and laptops come with recovery discs or a recovery partition on the hard drive that you can use to return your computer to the state it was in when it arrived from the factory. Of course, it goes without saying that you'll need to install your software again and you'll lose all your personal data, so you'll need copies of your important files (photos, university essays etc).
