Instead of commenting registry entries within the registry itself, you should export content that is about to be changed. That way, changes to values can be reversed by importing the .reg file you created - and you can comment .reg files, conventionally, by preceding a comment line with a semicolon (";" ). Note that importing a .reg file will not delete any new entries created since the export was made, so you should make a note of any additions so you can remove these manually.