Registry is a data base which stores configuration settings in Microsoft Windows operating system. It contains system settings, hardware and software configurations, and user preferences. Making incorrect changes in the registry can break your system. It's highly advisable to backup the registry before editing any portion of it. There are number of ways to do a back up of your registry but here I am describes the simplest and easiest way to the backup and restore registry using Registry Editor. Registry Editor is an advanced tool for viewing and changing settings in your system registry.
Backup the Registry
Windows XP
1. Click Start, and then click Run.
2. In the Open box, type regedit.exe, and then click OK
3. Locate and then click the key that contains the value that you want to edit
4. Right-click on the key and choose Export.
5. In the Save in box, select a location where you want to save the back up
6. In the File name box, type a file name, and then click Save.
Windows 7 and Vista
1. Open the Registry Editor by clicking the Start button, typing regedit into the Search box, and then pressing ENTER. If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
2. Locate and click the key or sub key that you want to back up.
3. Click the File menu, and then click Export.
4. In the Save in box, select the location where you want to save the backup copy, and then type a name for the backup file in the File name box.
5. Click Save.
Restore the Registry
Open the Registry Editor by running the command regedit, from the menu bar select File and click on Import, and then locate the backup file which you want to restore and press enter. If any confirmation dialogue box open click “Yes”.