Modifying the windows registry manually is a task are best handled by end users that are really knowledgeable in computers area. But before do any manual changes to Windows registry, it is advisable to take a back up. It is always a good practice for us to backup before perform manual changes on registry. Although most of the users know how to backup Windows Registry, but still some Windows users not aware about this. Follow below steps to backup your windows registry:
1. Go to Start menu search box then click run and enter.
2. Type regedit to Open Windows Registry Editor.
3. Click Yes if you are prompted with UAC (User Account Control) message. This may apply on windows 7 and windows Vista only.
4. On the left panel, click on My Computer. Click file menu then click Export.
5. You also can directly right click on My Computer and then select Export.
6. Enter a name for your Registry backup and click Save button. Done.
Source : Back up the registry