Computer isn't picking up SD card?

Okay, I have a brand new Targus card reader and an older Impact 128MB SD card from a Kodak Easyshare camera.  When I put the card into the Targus, it lights up.  The card reader shows up on My Computer as F but when I click on it, it asks me to please insert a disk.  This is my second time using the card reader - it worked just fine about a week ago the first time I used it.  Any ideas?  Tried to get it to read on my Compaq laptop and E-Machines desktop with no luck!
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