Hey there,
I recently got a new HTPC and installed Vista x64 on it to use the full 4 GM RAM in the PC. Vista came with drivers for my Hauppauge card (PVR 150 MCE) so it looked like a plug and play solution, but the card didn't work either in MP nor in the original Hauppauge app. You just see like 1 frame per secon and the picure quality is very very bad - an unusable situation.
After some research I found out that the combination of an x64 operating system and more than 3 GB RAM are the cause of the problem:
Hauppauge is not able to develop a working driver for these systems!
Hauppauge says, it's a Microsoft bug, MS denies this... So the situation is kind of stuck and I don't think a working driver can be exspected at all
So if you have a Hauppauge card, stay with x86 or don't buy more than 3 GB RAM, everybody else, don't buy a Hauppauge card!!!
Maschine