I have a windows 7 Pro PC where the current user account lost its administrative privilege all of a sudden.
In compmgmt.msc, I tried to add "administrators" to its group, but it fails. Please see the screenshots.
I tried to activate(unlock) native administrator account in compmgmt.msc, I got an error "access is denied".
When I tried to create a new account, I got an error "access is denied".
I opened control panel/User accounts and tried to add a new account "User" there, but I got an weird error like "The specified account name is not valid ...". Please see the screenshot above.
What can I try next?