After I plugged thew new card in, I found out that it doesn’t work too. I’ve checked all the wires and stuff and was puzzled by the fact that software seemed to be playing sounds OK, it’s just I couldn’t hear them.
It turns out that that computer has another sound card built-in into the motherboard. And after a reboot that I didn’t noticed it suddenly started to use that card. Simply by sticking the wire into another soundcard all the movie gunshots came back.
Note to myself: don’t assume too much. :)