Dear "anonymous" please try to be a bit more detailed to help people answer your question more accurately.
If you are looking to remove a password and you know what the password is, then follow the instructions above.
If you want to find out what a password is then remove it, go to http://ophcrack.sourceforge.net/download.php?type=livecd
, download the LiveCD iso for Vista, and burn to a blank CD. Then boot the computer in question from the disc. When the disc loads it will load into a linux environment which will automatically run a program which will crack the windows password and display it in a table in plain text.