Actually that looks exactly like a problem I just had to fix for a friend of mine who allowed someone (read scammer) to take remote control of his system.
The guy instantly ran "SysKey" google it. It's been around for a while like XP at least, maybe even earlier.
Fortunately
http://pogostick.net/~pnh/ntpasswd/
has a clear syskey option
Download, burn it to a CD, boot from the CD and read through the screens. Most of the defaults are fine, just look for the syskey option near the bottom of the accounts listed that you can impact.
Worked for me.