actually there is. i can switch them. like Carlosb said, windows just allowing one device at a time.. =(
Im not sure how you are actually getting sound coming from the DVI since its video only. Since my card has a mini-hdmi port, I use a mini hdmi adapter to hdmi adapter. That way I can be sure that sound and video will output to my connected TV.
Maybe you connected an audio cable from your pc to one tv and that explains why you were hearing the sound on that one tv and not on the other while still getting video output on both. If that's the case then you should get a splitter for your audio cable.