Hauppage used to provide a program called I think something like hcwclear which cleared out registry entries / unremove modules etc etc.
You are better off totally removing the old drivers
- especially if the new card is a QAM / DVB -S (Satellite) or even DVB-T (terrestial digital) receiver. - In most countries in W Europe (think the same is true in 'OZ / NZ etc old analog TV is being phased out / has already been phased out in favour of digital.
I'm not sure if Windows 7 supports any of the HD type TV broadcasts yet - "normal" Satellite works fine.
Here's a Satellite TV image from SKY TV with a Hauppage card . Running on Windows 7 X-64 Enterprise -- no probs apart from when I trip over the Dish cable after a nice "Goodnight" drink or two.