Richie, you'll need to search the web (the old web address I had no longer works) and get the manual. Put the system into programing mode (try prog 9999) and then power down the system. Follow the instructions to reset the user (and then engineer code) to default settings, then power up the system again.
Mike T
December 2011
Bin it, buy something a bit better.
Wont cost a lot either unless you want it for insurance.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home alarm systems.