Updating maps on garmin c340
You can try to write over the driver with the Garmin Communicator Driver.
To do this go to this web site (click the agree at the bottom of the page to get to the driver) and download the Garmin Communicator.
They offer a variety of mapping options at no cost. My older c340 recognizes the map "City Navigator North America NT 2013.40", but my newer c580 does not. 2013.40 is too tight a fit on the c580's internal memory, but 2013.10 is 220M smaller and fit just fine.
Maps are downloaded from the site and then installed on your GPS using Mapsource or Basecamp. A "City Navigator North America NT 2013.40" is 1.83GB. I had to delete all the voices I didn't use to make room, but my c580 map is now updated. As for my c340, there doesn't seem to be any reliable information on how to install a map in the internal memory.
So I have 2013.40 installed on the external memory card.
I'm using a Class 4 card so the map loads very quickly on boot.
Plus the C580 used MSN Direct for traffic which is now defunct.
The drawback of that is external memory draws more power, so using an external memory card is going to hurt battery life.
I have a Garmin Street Pilot c330 that is several years old. Disconnect the Garmin from your computer and install the program first.
Really - it is worth it to spend a little more to get lifetime maps and traffic on a new model which will have more internal storage and the ability to add a SD micro card.
Plus with Garmin now announcing the new HUD unit for around 130.00, it makes sense to investigate the models to get the best for your money.