Is there any mapping software what will display mulitple layered transparent maps on the computer, the way they would be viewed on a GPSr ?
You can probably do it with Garmin Mobile PC - it's basically a Nuvi for your computer. It isn't free however. https://buy.garmin.com/shop/shop.do?cID=139&pID=13484
If you want to try it for free, see if this trick still works: http://forums.gpsreview.net/viewtopic.php?t=10233