This took me a while to figure out, so I wanted to post just in case people were having trouble. When you are browsing the directories, you will find a place called "\mnt\sdcard". This is not actually your sdcard! This is internal memory. I was confused about this for days, thinking it was my sdcard, but it actually is not. To get to your actual external SD card, you need a file manager. I use File Manager HD, which was recommended to me on these forums. Now, to get to the right directory from File Manager HD, you click on "Storage" which routes you to /mnt/sdcard. Once there, you can hit the up-arrow at the top to back-out of that directory. Here, you see "External_SD" as a choice. THAT is your actual external SD card. You can use File Manager HD to copy files from internal storage (\mnt\sdcard) to your actual external SD (\mnt\external_SD). But you can never see your external sdcard on your PC when it's connected via USB... Hope this helps people who might be confused, trying to copy files onto their external SD.