I don't understand what's going on for you. When I attach my 7HT to my WinVista Box it sees both the Internal Memory (should be called Storage) and the microSDHC card as two drives and I can read and write to both.
Aaaaah... finally got it working... The answer was in "...as two drives..."
I have this one-track mind that the SD card would be located inside the A7HT filesystem itself. Copying some videos... have to wait more than 30 mins to copy some 6GB, which sucks.
Also using ES File Explore I can copy files from my PC to either Internal Storage or the microSD card.
Still need to figure out this one out, as well as the the "rw" thing.