If you forget your password in Vista you may reset it using Administrator account. But here is the problem - Administrator password is locked by default. So, at first you should enable it. To do this insert Vista installation disk into DVD drive and start your computer form CD.
After few moments you'll see following screen:
Click next and go follow to the next screen:
Click Repair your computer.
On the following screen click Command Prompt
You'll get black screen like this:
Type 1 and press Enter. Then type Administrator's password and press Enter. Usually Administrator's password is blank, so just press Enter.
As soon as you get following string: C:\WINDOWS>
type following command: net user administrator /active:yes
and press Enter. Then reboot computer and log on as Administrator.
Go to Control Panel -> User Accounts and Family Settings, then click on your user icon. You'll get following screen:
Click Remove Password and log off from Administrators account and login to your account.