To remove a user or group from the Permissions list
Open Registry Editor
Click the key whose Permissions list you want to change.
On the Edit menu, click Permissions.
Under Group or user names: , Click the name of the user or group that you want to remove from the Permissions list.
Incorrectly editing the registry may severely damage your system. Before making changes to the registry, you should back up any valued data on your computer.
To open Registry Editor, click Start, click Run, type , and then click OK.