Yume,
Wish I could answer your question but I've tried for months with NO success!
I have a Casio CTK611 and no matter what I tried I could only get the one drum sound thats on my pc soundcard.
What I've recently done was disconnect the keyboard from the MIDI connections and went with the LINE OUT from the keyboard to an amplifier...from the amp I go to LINE IN on my sound card.
Result: I can now record any sound my keyboard has built in and it also records as "Digital Audio" instead of MIDI.
One thing I have noticed is how powerful the drums sound now as opposed to the MIDI application.
I know this probably doesn't answer your original question..just thought I'd throw out some different options.
Rich