Are you sure - try swapping the two cards without changing anything else software (just the two cards - physically - remove the card from the one machine and swap it with the other) - they have the same chips so it's probably some leftover in the registry or some old dll or whatever - perhaps a codex or something - also i had to fool around a bit - installing in different orders rebooting etc. before i made it work.
I'll give that a try & Report back just looking deeper & found that the Medion card is the quad version & MP detects 4 cards (Other pc is running XP) This card (The Creatix one) only has 1 tuner in it (& This pc runs vista ) so should be interesting to see what happens. they both appear to be very different cards even though they are SAA 7131 cards.
I'll look around for the xp/vista drivers on the medion site swap them & see what happens
or I might look out for a nice quad card for this pc if all else fails.