If your speakers are connected to your FF (and not to a home-theater AVR with surround decoding), you'd need to send discrete 5.1 audio into the FF - likely using the Realtek's Analog Outs in to the FF's analog inputs - not very elegant IMO.  Otherwise, setting the default audio device to the FF 1/2 will only get you stereo sound - or an non-decodable bitstream if dealing with AC3/DTS bitstreams AFAIK...

Which part?  How would the FF400 decode a 5.1 bitstream if that is what the game is spitting out - or how would he get an analog 5.1 signal out of the FF400 into 6 discrete speakers if playing a video game?  I'm admittedly not much of a gamer - so maybe I'm missing something :-)  Getting a stereo L/R signal into the FF400 is cake - but I believe he is wanting to do discrete surround w/o involving a Dolby/DTS AVR for decoding (speakers are connected directly to the FF400). The only way I see is to have the Realtek decode to 5.1 analog, and then feed that analog back into the FF400's analog inputs - and out to the speakers.

I'm sure I've missed something - and I know MC will chime in with the answer :-)

Windows does all that automatically. And even better the newer the OS. And the Realtek does - of course - not have AC-3 decoding in hardware either.