I really advise against using 2 soundscards, getting the latency settings right so both cards play the audio at exactly the same time can be rather difficult, especially if your new to all this stuff.
His internal soundcard most likely only has 1x stereo out, and the usb device only has 1x stereo out. So currently he rather need the 2 sound cards, or needs to get himself a new soundcard.
Oh but answering the question, yes it is possible, you need to use asio4all for the drivers.