You can reboot computer to Safe Mode by pressing F8 during startup. Safe Mode is a troubleshooting mode that allows you to reset hardware drivers that might be giving you a black screen on your monitor. In Safe Mode you
Reboot Computer - YouTube Video
can use Device Manager to reinstall the correct video driver or other conflicting hardware driver. Then you can restart your computer normally with the video working.
The next reboot computer can reset your computer to its original factory settings by pressing F12 during startup (if your computer has this feature) or inserting a restore CD during startup. This will take an image and reimage your entire hard drive. This replaces all files including any saved files. This is not the best option because you will have to reinstall all your programs and other important files to get your computer back to a functional working state.
The last reboot computer option will restore your computer to a saved configuration that has all your important programs and files. This is accomplished using imaging software, such as Ghost or Partimage, that saves your current configuration and then allows you to restore all your important files when needed. I have YouTube videos on Ghost and one on Partimage. I also have a YouTube video on Reboot Computer that might be of help.
The Reboot Computer Help website has some additional information you might find useful.
Partimage - YouTube Video
Ghost - YouTube Video