Click Start> Run and type: control userpasswords2
The [User Accounts] Property Sheet displays.
On [Users] tab, clear the [Users must enter a user name and password to use this computer] check box.
Enter a user name and password that should be used to logon automatically in the dialog box that appears.
Go to [Control Panel] [User Accounts] [Change the Way Users Log On and Off].
Uncheck [Use the Welcome Screen] and [Use Fast User Switching]
Start windows in the SAFE mode by pressing the F8 key as your computer completes POST and before it boots into windows. Go to control panel and open user accounts, you should be able to change passwords there.