Map update - unit registration code needed?

I've got a StreetPilot c340. I'm planning to upgrade my map software to the new 2008 version. I bought my unit in March of 2006, so I don't expect to get a free update like many of you have been reporting. However, I don't have the unit registration code that came with my device when I bought it. When I buy the DVD to upgrade the maps, is that unit registration code needed to install the maps? Any info or advice would be greatly appreciated.

This is my first post, and I'd like to close it with a thanks: I recently upgraded the software of my C340 to version 4.30, and experienced the freeze-up and shut-down problems that are (by now) known so well to others. I didn't find any info on the Garmin support site about it, and it was after hours for their phone support, so I did a Google search and found this forum. I quickly learned that I wasn't alone with this problem, found links and instructions to backroll the software, and today found information about the new ver 4.40 software. So, thanks to everyone for being here! I love the Internets...