If you want modify any registry key on windows 7 you will need permission to do that because, you have to verify yourself to make changes to it so here is how:
1. Go to Start -> Run and type in regedit to open the registry.
2. Navigate to they key directory that you want to get premission to and make any changes for example we’re going to use HKEY_LOCAL_MACHINE -> SYSTEM -> ControlSet001 -> Enum then right click on it and click premissions.
3. On Permissions Dialog Box click Advanced.
4. Now go to Owner Tab and under the change user to: select the current user you’re logged in and then tick Replace owner on subcontainers and objects and click Apply and Ok.
5. Now you can modify the keys on that directory depends what you’re using