I acquired a Tom Tom satellite navigation unit early last year (I say "acquired" since I used points from my American Express) and I've generally been quite happy with it. At least happy enough that I purchased additional maps for a trip to Australia earlier this year, and just recently I purchased more maps for a trip to South Africa.
I'd managed to successfully install and use the Australia maps and followed the same procedure for the South Africa maps, so I was a little surprised on driving out of Johannesburg airport that it failed to show our location on the relevant map.
I eventually discovered after browsing some of the configuration menus that you have to tell it which map to use. It hadn't even occurred to me that this was the problem. Not for a second. Not even a nanosecond. Why not? Because it's a damn GPS unit. It knows where the bloody hell it is. That's what it does. That's its karma. And if it knows where it is, it knows everything it needs to know to automatically select the right map to use! I just didn't imagine for a second that any half competent software designer would have designed it any other way. So I've come to the conclusion that since Tom Tom is a Dutch company that Tom Tom must be Dutch for Dumb Dumb.