The capacity of the card won't be 2GB exactly.
I love your threads, you make so many of them, you have brilliant titles, it brightens up my day.
Knowing you, you've bought a cheap sd card off eBay, and it's a fake and might say it's a 2gb cars but infact it's a lot smaller as it's fake.
That's my theory.
Even ones on amazon from the 'traders' on there are mostly fake.
Have you got maps on there for your nav then and windows can't see them as they are an unknown format and so thinks it's empty?