By default, Windows 7 doesn’t show empty drives like card readers and what-not in the explorer window. As far as I know there isn’t really a good reason for this, so I keep it so everything shows up no matter what.
Click Start, and in the Search Box (Located above the Start button) type “Change search options”. In the results that will appear above, you’ll see a selection at the top that says “Change search options for files and folders”. Click it.
Now select the View tab and scroll down until you see the selection that says “Hide empty drives in the Computer folder” and un-check it. Hit Apply, then OK and you’re all set! Now whenever you insert media into your computer it’ll show up regardless!