You could download Hiren's boot cd which contains a password removal. I don't remember if it worked on vista though. If you don't try hiren's then the only way is to do a factory restore, which will erase are your data and have your computer running like it was new. You can still back up your data before you do this but you would need to open the chassis and take out the hard disk drive. What is the manufacturer of your PC? HP, COMPAQ, ACER, GATEWAY, SONY, DELL, TOSHIBA, LENOVO, VELOCITY?