Pretty sure you're out of luck. I can't even find the hardware on Pinnacle's site, let alone updated drivers for the card. These are things you need to take into consideration when deciding whether or not to upgrade. Since Microsoft is killing support for Windows XP next month, I'd suggest it's time to get a new TV Tuner card that is Windows 7 compatible.
Not what you want to hear, I know, but that's the best advice I can give.
-Wolf sends