Well, isn't this obvious? This is known since a long time and a base of every defense in depth concept you are building.

If there are really security companies supporting statements around this, you probably shoudl think twice

Roger's Security Blog : Windows Vista Recovery Console and the Password: http://blogs.technet.com

What OS are you having?

On xp you can try this:

Boot computer and press Ctrl+Alt+Delete twice when you See Windows welcome screen / login screen. It'll show classic login box. Now type "Administrator" (without quotes) in username field and leave password field blank, press Enter and you should be able to login Windows.

Now you can reset your account password from "Control Panel -> User Accounts".

On win 7 or vista:

Ctrl+Alt+Delete won't work, you have to use some windows password recovery software. I recommend Windows Password Recovery Tool 3.0 .