Man, am I an archeologist or what? Thought I'd throw this in, since this is nearly the first result of you Google the Zumo 550 SD capacity. If you're on a Mac, or have Cygwin on your Windows computers, you can easily count the number of songs you have on an SD card using terminal - Open Terminal.app - Put your SD card into your computer - Type this: 'ls -l /Volumes - look at the output and find the name you've given your SD card - Type "find /Volumes/YOUR_SD_CARD_NAME_HERE/music/ -name "*.mp3" | wc -l" The output will be the count of mp3 files in the 'music' directory of the SD card. Example from my 4GB SD card has 3.6GB of songs on it, mostly 128hz bitrate, the typical bitrate for ripped or purchased songs). Doing "find /Volumes/5504GB2/music/ -name "*.mp3" | wc -l" will output "648". Given that, I think an 8mb is about the max if you're interest is just having room for music. If you're keeping your stash of Jayme Langford photos on your Zumo , just keep in mind you'll max out the 1000 song limit somewhere around 6-7GB. For windows it would be something like 'dir /a-d /s /b music | find /c ":" from the command line (once you had used 'cd' to get to the right directory on the SD card). For you Windows users without command line experience, I think using the UI you can get the properties of a folder, and it shows a recursive file count there.