If you have enabled password protection to in your pc via the Windows Log in screen and any chance have forgotten the password then here is one trick you could use (though here already posted many more articles about how to retrieve missed password… you can try search feature also..) … this trick successfully works on Windows XP, however you can also try it on Windows Vista or Seven and let me know whether it works or not?

Form the Windows Logon screen (ie whr u have multiple user account or a user account having password)
Press Alt+Ctrl+Del (2 Times)
You will get a seperate window… Write
User : Administrator
Password : (Leave it Blank)

Press OK…

Now you are logged in…as a Administrator…

Note: This Trick cant be use if ur account name is “Administrator”…

Enjoy….