Your account is probably labelled as "Computer Administrator". However, there is a default account installed by Windows setup called simply "Administrator" with no actual user name attached to it. It cannot be deleted. This account is normally hidden at the log-in screen and in the User Accounts applet of Control Panel. To make it visible you have to boot into safe mode where it will then be visible in the log-in screen.
However, it will probably have been protected with a password, so unless you know the password you won't be able to log-in to it.
Edited by pip22, 23 March 2007 - 08:15 AM.