This thing is killing me. I connected it to my computer with the USB cable that came with the phone and Windows Vista is not recognizing it.
Did the phone come with a disk? Also check the website for the phone, the drivers may need to be downloaded from there. I had to download a syncing program for my phone in order for my PC to recognze it.
You can get the Galaxy S driver from here after you install it, then your computer should reconize the memory card after mounting it from your phone. Hope this helps you out.