I have two S3's mine and my wife's. When my wife's is plugged in to the PC via USB both her internal and external SD cards show up in Windows Explorer and you can easily transfer files back and forth. When mine is plugged in you cannot see the SD cards show up in Explorer. Did the soft reboot and factory reset on the phone and no drives show up on Explorer. USB cords work fine. Different USB ports do the same thing. Tried 3 different PC's with my phone and none of them showed the phone in Explorer. Samsung's Chat help couldn't help...Samsung's Phone Support couldn't help...AT&T replaced the phone. New phone, still no luck. The only difference between my phone and my wife's is that mine has the UCLG1 update and her's doesn't. I've tried Kies and it also apparently doesn't work with the S3. I haven't tried Kies Air yet. Any other suggestions or is the update what is keeping Explorer from seeing my phone?