Show The Hidden Administrator Account In Windows

As you know there is a default administrator account in windows xp, vista and windows 7.
Generally this administrator account is disabled and one cannot use it. But this can be shown  
with the help of command prompt.

For this follow these steps:

First you go to the command prompt from accessories from the start menu.

Then type this command:   net user administrator /active:yes
then press enter.

Now you can see it at your logon screen.

To deactivate this just change the yes parameter to no.
  net user administrator /active:no