:israel: Yes it is possible to change Adminstrator password both in Win XP and Vista without knowing it. If you somehow manage to login as an Administrator then you can change the password without knowing it. Heres the Step-By-Step instructions 1. Right-click on the My Computer icon on the desktop OR in the Start Menu. 2. Select the option Manage. 3. On the left pane expand the Computer Management (Local) tree (if it is not already expanded) 4. Double click Local Users and Groups option From System Tools tree. 5. Click the Users option. 6. Now you will see the list of users on the right side pane, such as Administrator, Guest etc. 7. Right click the Administrator and select the option Set Password option. 8. Now you will see a warning message, Click on proceed. 9. Now the system asks you for New Password and Confirm Password . 10. After entering the password click on OK. The password is changed. Thats It!