Every time you download a game, movie, etc to your computer, you make changes to the computer. Sometimes, these downloads can make your computer unstable. By default, Windows Vista creates restore points in the background. What this means is every time you make these changes to your computer, Vista takes a snapshot of your computer before the changes are made. This enables you to go back in time and restore your computer to an earlier time. Documents, photo's and emails will still be saved. Open the start menu and type system restore and press enter. You can choose the restore point. You can create restore points when you know you are going to change your system, so you have the option to go back.