This was one of those, odd, shouldn’t be possible, situations (ever try deleting system32?). A Windows 7 machine had a Standard User account, and the Administrator account (not the “hidden” one) was not accessible. Trying to run a program as another user (holding the SHIFT key) and typing in the credentials didn’t work, I was met with “The service could not be started…” the fields to enter the credentials were missing. The first thing I tried was unlocking the account; I used Locksmith, and it said it “enabled” the admin account, but still no dice. I enabled the the “hidden” administrator account but after restarting I could not access that account either.
Now, for the kicker, I was told the user followed this tutorial (http://www.mydigitallife.info/how-to-create-hidden-user-account-hide-user-account-from-welcome-screen-in-windows/) to hide the admin account, if you read the comments you will find that everyone who tried hiding the account locked themselves out, my scenario.
Basically, you add a couple keys and corrupt the Winlogon key. Well, I wasn’t going to waste my time here so I booted Petter Nordahl-Hagen NT Password Reset off my flash drive, unlocked the hidden admin account, rebooted, and low and behold, I could log in as admin! The first thing I did was open regedit and delete the added registry keys and then for good measure, I restored the system to a date prior to the registry keys being added.