1. Back up your entire registry by either exporting it to another file name or saving it to an external device, such as a USB flash drive, external hard drive or a CD. Hopefully you won't need this, but it's better to be safe.
2. Set a system restore point in either Windows XP or Vista. This allows you to go back to a stable system that existed before you edited the registry.

3. Click on 'Start' and type 'Regedit' in the run field, or in Vista, click on 'Run' and then enter 'Regedit.' This brings up your registry editor.
4. Know specifically what you need to change. The Windows registry is huge and navigating it line-by-line is almost impossible. You can also search the registry for specific keywords related to your problem.
5. Select the area you need to edit from the left pane of the editor. Lines of code will appear in the right pane, where you are able to make your changes. Be careful not to make a mistake.
6. Save your changes. Close the editor and reboot. Any changes you made will become effective during the boot-up process.