MAKE YOUR LIMITED ACCOUNT ADMIN VIA COMMAND PROMPT

To do so, you need to open the command prompt in admin mode..

Goto Programs -> Accessories -> cmd
Right click on it and select run as.
Select run as following user and provide the admin's username and password.

Now command prompt will open. In that add this command...

c:\..> net localgroup administrators /add

You have to add the account name in place of   and then press enter.

Now Logoff and again login.

You will be administrator now......  :)