I am not computer savvy when it comes to booting, etc. I am very hesitant to try anything.
Here is one thing you can try if you have access to another computer with Vista.
From Microsoft:
http://windows.microsoft.com/en-US/windows-vista/Create-a-password-reset-disk
Worked for me - send me a private reply with your e-mail addy and I will send you a Word document I wrote about this. It will step you through the process ...