2 GB MicroSD Card Not Reading.

I just ran out and bought a SanDisk 2 GB microSD card for my Express. To test it out, I put the card into the Adapter and threw it on my computer to put some songs on there. Got 3 songs on there, took it out and slipped it into my Express. Turned it on, went to music and played but the only thing that came on was the music I already had on my Express already. This confused me because at one time I put my 8 GB microSD card from my phone into my Express, it booted up but it was extremely slow in doing so but it read the card and played them. Even though it took a bit to do so.

So I have to ask… what did I do wrong?