The only problem I've had with my Hauppauge 1600 was when I had to move it to another slot, I had to go through the song and dance with MC again in setting up the card and guide. A bit of a pain, but no big deal. I've never had the problem you're having, even with Vista.
Changing the card completely will probably mean an uninstall of the drivers, then putting in the new card and letting Windows find it. When I built my Seven machine, that's all I did. I've since moved slots in Seven, too, b/c I just seem to enjoy pain and anguish or something, but there weren't any problem there either.
I can't see why MC would break, unless you did the QAM registry hacks in Vista. I gave up on QAM here in Canada. I can't get MC to let me set it up.