When Vista first came out I had to help someone who bought a refurbished Sony laptop and it was in a middle eastern language for some reason!
I found a program called "Enable Admin.exe" that allowed me to enable the admin account. I had to do this by getting into a command prompt by using the Vista disk and once there I was able to get to a USB flash drive and run it.
Not sure if that will work or not with service packs on Vista as I believe they might have provisioned something to stop that.
I know there's a way with XP to get in and change passwords during a repair installation but doubt it works with Vista..