Log into Windows in you normal account.
1. Click Start, and then click Run.
2. In the Open box, type "mmc" (without the quotation marks), and then click OK to start MMC.
3. Start the Local Users and Groups snap-in.
4. Under Console Root, expand "Local Users and Groups", and then click Users.
5. In the right pane, right-click Administrator, and then click Set Password.
6. Click Proceed in the message box that appears.
7. Type and confirm the new password in the appropriate boxes, and then click OK.