if you mean the windows password then try logging in with the user name administrator and no password (it's shocking how many people don't set an administrator password!)
There's a way to reset Administrator password and it doesn’t involve reformatting and reinstalling Windows. The solution is called Windows Password Reset 7.0. It can reset almost all Windows passwords in seconds. It is a great windows password recovery tool: http://www.resetwindowspassword.com . you can log in again just in one second. It also support windows 7 password reset.