Manual steps to export registry subkeys
You can follow these steps to export a registry subkey before you edit it.
Note Do not follow these steps to export a whole registry subtree. (HKEY_CURRENT_USER is an example of such a subtree.) If you must back up whole registry subtrees, back up the whole registry instead.
1. Click Start, and then click Run.
2. In the Open box, type regedit, and then click OK.
3. Locate and then click the subkey that contains the value that you want to edit.
4. On the File menu, click Export.
5. In the Save in box, select a location where you want to save the Registration Entries (.reg) file, type a file name in the File name box,
and then click Save.
If you then wish to change it back, go to the saved registry value and double click it. Answer "Yes" when it asks you if you wish to merge the value with the registry.