Need help for added regions

I have a UK PIN 570 and have just bought the North American Maps for use on travel. I have loaded them and activated the maps.

The question is how do I know for sure they are going to work.

When I use the GPS system here, it loads the uk maps etc and on the PDA itself it does not have the North American maps on the active list. On the desktop SMART software I can see they are on the stored memory so how does that work.

Any advice would be helpful.