my guess is look on the manufaturer's website...if you don't list a model, no one can help you.
also, TV tuner card drivers are one of the first things to check before making the jump to 64bit. you should've checked that before you went 64.
if its too old get a new one
try windows update - most are supported there
also try manafacturers website
You havent told us what you have so theres no way for us to help. Follow apache_lives' advice and check out the manufacturers website. If all else fails, I just set my parents up with the Hauppauge 2250. Works perfectly under 64bit Windows 7.