Why isn't my new PNY 2G Micro SD card adapter not working?

I recently bought a Blackjack II. I decided to buy an SD card for it so I could have my music and etc. on hand. So I went to Best Buy and bought a PNY 2G Micro SD card with an adapter for it. When I got home I decided to try it out. I put the card into the adapter and set it into the correct slot on the computer, but it wouldn't recognize it. I tried the SD card in my friend's adapter, and it worked fine, so I'm guessing the problem is with the adapter.