This isn't a Vista specific problem (not even Windows specific). On every OS you will be able to bypass any kind of security when you have physical access to the machine, unless the files are strongly encrypted (and even that isn't fail proof).
andrew's suggestions are with checking out. But, keep in mind encrypting/decrypting the files will decrease performance a bit as your CPU need time to handle the files.
quote:
Originally posted by Chancer
Did you try "format C:"??
I assure no one will access your information.
Actually, you could still get the data after a format
.