Help Not all directories under /mnt/sdcard appearing on PC


I just moved from a HTC Desire to Xperia S 32GB. One thing giving me headaches is file management on the PC (when connected via Sony's PC companion). There are directories I can see via Astro on the phone but not on the PC in the Internal Storage area (the only area exposed to the PC).

I use FuelLog that exports data to /mnt/sdcard/FuelLog and I can't see this directory on the PC. I need this so I can import data from the last 18mths back into FuelLog.

Why is it that I can't see some directories (this is not the only one I can't see) on the PC?

Also there seems to be a /sdcard and /mnt/sdcard on the phone (see via Astro). Are these the same directories and one is a symbolic link?

Lastly what's the deal about "USB Storage" (under Settings | Storage)?

many thanks