I had the following experience updating the maps on a Garmin c530 GPS. Purchased about two years ago, I decided to update the maps since there have been a couple of situations where new development and roads really fooled the GPS.
The update was for the North America maps. I could not purchase the update on the internet because internet Garmin products are only sold to US and UK customers. Arranged with The Source to purchase the DVD and when it arrived I tried to update the GPS unit. Found out that the GPS would only accept either Canada and the Border States or the Lower 48 States. After a couple of emails to Garmin Customer Support, I purchased a 2 Gb SD card, downloaded the maps from the DVD to the SD card, put the card into the GPS unit and now I have the updated maps for North America. Apparently, the internal memory in the c530 unit is too small to handle the amount of information in the new 2009 update.
Just a bit of trivia for those with the similar GPS unit.
Nestor