Ok, if this is answered somewhere else then I'm sorry but I can't figure this out. I have the Magellan Streets program and have made detail maps for my Explorist 500 before, but it has been a while since I'd done it. They worked fine. I tried to make one last night and when I clicked to upload to GPS, then save to HD, it saved it as an *.img file. It skipped the step of asking my serial number so I think somewhere, somehow it's not getting it to the *.imi file. WHY???? *banging my head on the desk*. I even tried re-installing the software and it still won't work, I can't even test the GPS unit because I hook up through USB, not the COM ports. This is very frustrating, please help!!!!!