First,you can try this method.Start system and press F8 key when Windows is starting up. Then select Safe Mode with Command Prompt and enter. Choose Administrator,the default password may be blank if you don't set the default administrator password before.Then you will enter into doc Command as following.
Type " net user net user xxx 12345 /add " (xxx is the locked account name and 123456 is the new password set on this account).Then you will see the Command Completed Successfully.
Then this method can fully help you remove the administrator password,i highly suggest you this one.
1. Login to a computer that can link to Internet. Download windows Password key from http://www.lostwindowspassword.com
and install it on that PC. Note that: there is a .ISO file. Burn the .ISO file to a CD or a USB flash drive.
2. Insert the newly created CD/USB drive to the locked computer.
3. Reboot the locked computer and press'F2'or'Delete'to enter your BIOS setup and then followed the process of instructions. Just a few steps, the old password was removed.