1. Open User Accounts by clicking the Start button , clicking Control Panel, clicking User Accounts and Family Safety, clicking User Accounts, and then clicking Manage another account Administrator permission required. If you’re prompted for an administrator password or confirmation, type the password or provide confirmation.

Your account type is displayed below your user name.

If your account type is Administrator, then you are currently logged on as an administrator.

If you navigate the windows explorer over to c:\users you will find a list of all of the users on the computer, may possibly lead to you the username of the admin.