Hi Lee,
I had a similar situation a while back and I solved by disconnecting all power from the system including any backup battery in the control panel ( the outside siren will sound). Leave for 15 mins then reapply power. This is a complete system reset and will default to the original factory settings. The code should then be 1234 or 0000.
If you contact AEI in Rye, they should be able to let you know how to change the password. Hope this helps
Peter Langley
December 2009