reboot computer
The need to reboot computer occurs when either the computer fails to start-up properly or you need to reinstall or restore the operating system because of various issues. You need to understand Windows is a large complex operating system that requires regular maintenance to keep functioning properly. When your computer freezes or hangs the problem could be a registry issue or a software driver conflict. Sometimes just rebooting the computer will allow the computer to run again. However, the underlining problem still exists and will reoccur. There are several good registry cleaners found on the commercial and free Open Source markets. You might download a free or trial version registry cleaner to see if the problem can be easily corrected with one of these utilities. For the software driver issue you will need to visit the manufactures website and review the support documentation to find any available fixes or updated software drivers that can solve the conflicts.
Safe Mode
You can reboot computer to Safe Mode by pressing F8 during the start-up. The Safe Mode is a troubleshooting mode that allows you to reset hardware drivers that might be causing a black or blue screen on your monitor. In Safe Mode you can use the Device Manager to reinstall the correct video driver or other conflicting hardware driver. Then you can restart your computer normally with the video now working.
Original Factory Settings
You can reset your computer to its original factory settings by pressing F12 during start-up (if your computer has this feature) or inserting a restore CD during start-up. This will take an image and re-image your entire hard drive. This will replace 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.
Imaging
Another option is to 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 several YouTube videos on Ghost and one on Partimage. I also have a YouTube video on Reboot Computer that might also be of help.
The Reboot Computer website has some additional information you might find useful.