prepare your Windows 7/Vista DVD and restart the computer with the DVD in the DVD Drive—you’ll want to boot from the DVD so you may need to change the boot order in the BIOS. Depending on your system you will need to press Del, F2, or F12. After you’ve successfully booted from the DVD you’ll be presented with the language setting of the Windows setup.
Click next.
In the next screen click “Repair your computer” from the bottom left corner of the window. Now the setup will search for Windows installations then display them, choose the Windows you want and click next. The setup may try to search for problems and may ask you if you want to restore your computer, just click no. Finally you’ll arrive at the System Recovery Options
select comand prompt
in that type regedit
go to file>load hive
In the file name field type the following and hit enter.
%windir%\system32\config\SAM
The hive needs a name, give it a name and remember it. For the purpose of this article we will name it “test” so replace it with the name you chose for the next steps. What you just did is load the SAM file into the Registry Editor so we can edit it. The SAM file is the Security Accounts Manager and contains encrypted information about the account names and passwords. Now that it’s loaded into the registry, navigate to “HKEY_LOCAL_MACHINE\test\SAM\Domains\Account\Users”. Click on “000001F4” and from the right side pane double-click the “F” entry.
A new window will open allowing you to edit the “F” entry. The line that starts with “0038” is what you want to edit. The value next to “0038” is “11”, replace it with “10”. Be careful not to change anything else. Just double click the “11” and type “10” then hit the OK button. “11” is for disabled and “10” for enabled.
Back in the Registry Editor, from the left side click on the name you gave to the hive you loaded earlier and click “Unload Hive” from the File menu, restart the computer and you are done. The Administrator account is now enabled.