How to backup and restore the Windows Registry ?

To backup certain keys in the Windows Registry:

1. Click Start -> Run, and type: regedit
Note: You can choose a subkey at this point, if you prefer to only backup a part of the registry.

2. In the File menu of the Registry editor, click Export to backup, or Import if you'd like to restore a previously saved file.

3. Type a filename, choose the location where you want to save the file, and click Save

Warning: Even though the above method works well for backing up parts of the registry, it is useless for making a complete backup. It does not export the entire registry (for example, the "SECURITY" hive is not saved), and the exported files can not be efficiently used later to replace the current registry with the old one. If you re-import the file, it is merged with the current registry without deleting anything that has been added since the export, leaving you with a mess of old and new entries. For exporting the complete registry, look into: Start > Programs > Accessories > System Tools > System Restore, or you can try using an external program like ERUNT, or you can read the MS Articles below.

For additional information on backing up the Registry and the System State, see the links below:
MS KB 132332 - Windows 95
MS KB 128731 - Windows NT 4
MS KB 256419 - Windows 98/ME
MS KB 240363 - Windows 2000
MS KB 320820 - Windows XP Home
MS KB 322756 - Windows XP / Server 2003