How can I tell what is in the internal memory of a c530?

I know this must sound odd. When I went to install the North America 2008
update in my c530 it claimed that there wasn't room in the internal memory for
the whole thing, and that I would have to chose the US 48 states or Canada,
Alaska, Hawaii and some chunk of the US states near the Canadian boarder. So I
installed the "lower 48" in the internal memory and then loaded the other bunch
(overlap and all) onto an SD card. It worked just fine, with the two maps
treated as one.

In trying to add some new maps (see my recent post) I pulled the SD card and
played around with the unit. (I wanted to show my wife that the northern parts
were missing.) To my amazement it promptly plotted a route from New York to
Anchorage. So I suspected that I had the two parts mixed up, and had the lower
map on the card, but then it also plotted a route from New York to San Diego.

So, I seem to have more in the internal memory than I was told would fit. How
can I find out exactly what IS there, so I can avoid having to add duplicate
stuff to the combined SD card I'm making?