You created a brand new Admin account, it could update (meaning permissions were intact and working) you logged off, the next time you logged in the permissions were messed up for the new account. It just smells fishy to me, if this were my computer, I would suspect that my system was compromised, rooted, and/or backdoored. That basically means a malicious peice of software compromised your system, then covered all it's tracks and made a way for your box to be accessed and controlled at someone's whim. With your box being very behind on updates it stands to reason it would have been susceptible to known exploits which may allow this kind of thing to happen. Just because your computer passes a virus scan does not mean it's clean. It's also possible something is just wrong with your computers configuration, my Windows knoweldge isn't very high so I can't really add much to help with checking that.