The windows registry contains critical settings for all your applications to work. So when ever a registry entry is deleted or manipulated it is always a good practice to back the registry before doing any work with it.
This will ensure that you do not loose any critical data.
For backing up a particular registry entry do the following:
Open the registry editor. (Start > run > regedit)
Navigate to the registry key you want to back up before editing the key.
Go to file > export.
In the export registry file dialog box, select the export range at the bottom to either ALL or the selected branch alone.
Select the location to save the file.
The registry files will be saved with an extension of .reg.
Now suppose you have manipulated the registry file after exporting and backing it up and if the file gets corrupted, you can always bring back the registry file back to its normal form by just double clicking and merging the registry file which you have backed up in prior.