All you need is a Vista Install DVD and you're all set to go.
- Just boot from the DVD and select the Repair option.
- Then select the Command Prompt.
- And you'll end up with an Administrator priviledged Command Prompt.
This kind of reminds us of a Windows XP Home feature. The Administrator account password for XP Home is blank by default and is hidden in Normal Mode. But if you select F8 during boot for Safe Mode, you can access the Administrator account and have complete access to the computer.
Physical security of your computer is paramount.