|If you can use another computer, download OPHcrack live CD for Vista and burn to a disc.|
Start your computer and have it boot from the CD. OPHcrack will run and tell you any accounts that are on the computer as well as the passwords. it will take a little while to run.
You can then see if your account is still there and what the password is, or some other account which you can log on to windows with.
Or download ultimate boot cd and burn to a disc. boot from the cd. With ultimate boot cd you change the passwords for user accounts on the computer - this more advanced as it is a command line utility.