EvilZone

Hello , this is my first time posting on this forum. I have a computer that has 1 admin account, the one (locked up) owner forgot password, and also has another regular user account (no admin rights), which is the only account that can be accessed at the moment.
I have already tried net user commands, to try and remove the pass , with no success, always get Error 5, access denied.
I have tried to Enable the hidden admin account on Vista using Computer management, but I get the same error.
It seems the only way would be a tool to crack into it.
Any suggestions will be welcome, thanks in advance.