The Ax doesn't have the facility to easily transfer from PC via USB most people move files using memory keys or if you wnat to use the AX to read the files I usually usea Jump Drive Trio, insert the SD card and attach it to the usb port copy the the files and insert it back in the AX. Any card reader will do this for you but I use a Trio for convenience.
http://www.everythingusb.com/hardwar...Drive_Trio.htm
Hope this helps.
ps. buy the largest SD card your budget will allow - Kingston or Lexar are my favourites, no problems very reliable.