You can only have TopoUSA on two computers at once. I learned that the hard way.
When I got my PN40 at the end of last year, I immediately loaded Topo7 onto both of my home computers. This year, I got a laptop computer and loaded Topo 7 onto it. In the meantime, I had forgotten that I loaded Topo7 onto the computer in the den (short term memory is the first to go y’know).
When I went to the map library to download aerial images onto the laptop, the program wouldn’t let me—anywhere in the United States. The map turned gray and indicated that coverage for the area was unavailable.
I went back and read the fine print on the license terms that you always agree to without reading it. It said that the program can be used on just two computers—presumably one at home and another mobile one.
So, I uninstalled Top07 on the first computer (never used it … that’s why I forgot it). Subsequently, I could tap into the DeLorme map library and download images with the laptop. Obviously, then, those sly devils at DeLorme keep track of the number of computers from which you access the map library, and cut ya off at two.
The moral of the story is don’t space out like me and lose track of where you’re putting those Topo programs.