Members of this forum are kind of reluctant to help anybody with password issues.
Are you the original owner of this computer?
Do you have an account registered with Microsoft. Such as an e-mail account on Hotmail or Outlook? A common practice is to use the same password for the e-mail and the computer log in.
Now then, here is what you might do. Try to reboot in the safe mode. This is done by hitting the F8 key early in the boot up. You should get a log in screen that lets you use the system administrator.