Prior to editing a value in a registry key, use Regedit's Export Registry file capability. Start up Regedit, browse to the registry key you will be editing. Prior to doing anything else, click on the key, click Registry/Export Registry File and save the current key's contents into a .reg file. If things go wrong, get back to where you were by double-clicking on your .reg export file. Create a standard location for .REG files. See .REG for background information on .reg files in general.