This type of message can be caused by many different things. Your first step should be to boot into Safe Mode and see if you can get into your computer because Safe Mode uses a generic Windows driver rather than the one used by your video card in case its a video card driver issue. It will also allow you to run MSconfig and disable some or all of your startup items in case the error is being caused by a program or some type of spyware that is running in normal mode.
Since you may not have access to your USB ports or CDROM in Safe Mode to back up your files then you can hopefully get your computer to a point where it can boot ok normally. If you do then you can backup from Safe Mode.
If you do a Windows System Restore it wont affect your files/documents. It only puts the computer back to state where it was at that point in regards to the Windows configuration. If you do a system recovery with your recovery CD then that will wipe out your files.
Keep in mind that this error can also be caused by bad RAM so you may have to try taking out some of it if you have multiple chips and finding a combination that works.
It may also be caused by spyware so it would be a good idea to run some scans in Safe Mode as well. There are many free tools and software you can use to do a good job of cleaning your computer.