There are two possibilities. First, and least attractive, is that the game damaged your windows installation and it can no longer boot in 'normal' mode. You can try the following to see.
When you start the computer, press the F8 key before windows comes on. This will give you the 'Startup Menu' on a black screen. Choose 'normal mode' or 'Start Windows Normally' if the option is present. If there is no choice for starting windows in 'normal' mode, you have a damaged OS and must reinstall windows. If windows starts and runs normally, you were just stuck in 'safe mode' by the start options which the game caused, and should have no more problems. I hope the second option is the one that occurred, because otherwise you'll have to back up your data externally or on another hard drive. When you reinstall windows you lose everything on the primary hard drive.
