Restart to main login screen

Greetings,

We have an issue accessing our admin account and due to a series of events - cannot access the login screen.

Below is what was attempted to reset the password and the current status.

1. It followed steps here http://osxdaily.com/2010/08/10/forgot-mac-password-how-to-reset-mac-password/ to "Boot into Single User Mode and remove a setup file" - this was done as the original discs had been lost

2. Turning the machine on bypasses the login and continues straight to the "setup process" for new machines.

3. The original discs were found a day later and if we try and reset password from the discs, it only offers the disc drive to reset and not the machine

Current Status:

Our IT department (located in another country) cannot find the serial number so we cannot complete the setup process

Question: Can we use a command in the terminal (through the Single User Mode startup) to return to the login screen or can we but a new license key?

Thank you all - it is an unusual circumstance.