A GPSmap 76S has a fixed 24 MB of internal memory. You cannot expand this or use memory cards. Some mapping products use an unlock code. The unlock code is specific to a particular version of a particular mapping product and a particular GPS serial number. You can load somebody elses maps to your PC and enter their unlock code and it will let you view them on your PC but you will not be able to load them to your GPS. You can borrow somebody elses MapSource map CD and load it to your PC and then enter your unlock code (as long as it is for the same map product and version number) and this will work .