When you change the keys or values of the registry, Registry Explorer  makes a backup files. If you decide to restore the old value or key just click on the "View Undo" button.
The window with the history of your actions will appear. Find the row with the action that you want to undo and right click on it, then choose "Undo" and that is all.


Related Topics: What is RegExp, Keyboard Accelerator, Bookmarks, Searching.