The way I've made a backup is to copy everything (files and folders) on my SD card into a folder on my pc. I routinely do this before/after version and map upgrades. I used this method to migrate to a larger SD card. Just copied the backup files from my pc to the larger SD card.
Thanks sally it will be next week before I get round to a back up.
Can I ask why do you have to put the card in the cars NB1?
And I assume it won't stop the original from working?