Depending on how you setup you computer, the default “Administrator” account may be disabled. To enable the account again, you can use the Local Users and Groups management console built-in to Windows.
The easisest way to get to the Local Users and Groups is to:
- Open a Run… box either from the Start Menu or by holding down the Windows key and pressing “R”.
- Type “lusrmgr.msc” and press enter.
- Click on “Users” in the window that opens.
- Double-click the “Administrator” user listed.
- In the window, remove the checkbox from “Account is disabled”.
- Press “OK” and close out of any remaining open windows.