So today I was troubleshooting why a local scheduled task to back up a SQL Express database hasn't been running. Oddly, in SQL Server Management Studio (SSMS) I could see that the sa account had been disabled, and that only the 'builtin/Users' account had login rights. BuiltinUsers didn't have admin rights, either.
Hooray for this post over at mssqltips.com, which allows you to leverage psexec to get a SSMS login under the NT AUTHORITY/SYSTEM account, and then change the permissions. The command is this:
PsExec -s -i "C:\Program Files (x86)\Microsoft SQL Server\110\Tools\Binn\ManagementStudio\Ssms.exe"
You may need to modify the path, and you need to run it from the SQL Server itself after copying PSTools over to the SQL Server. Also, this command is all one line, and there is a space between SQL and Server. I don't have the time to fight a formatting war right now....
I highly recommend that admins keep a copy of the various PSTools programs around, as they can be very handy. I even found a GUI front-end for them.
This is also a stark reminder that you can lock down an application as much as you want, but the minute someone gets admin access (or physical access) to the system itself, all bets are off.