Hi I just purchased a map update for my device,and I'm having a hell of a time to install it on my tom tom go. Tom Tom Home says that I don't have enough room but I can install zones instead of the whole map but whenever i try to find information to install zones a hit a wall. I only want to install a zone that covers Eastern US and Canada. I already have a 128 mb sd card in my device, how big of an sd card can I use on my device? I'm going nuts, have been at this for about 2 hours! I dread each time I have to update my device, please help me!