Pinnacle tv tuner cards are crap...and this is not just from my personal experience only, but from many others including quite a few from this forum. Don't bother with their buggy software, its a nightmare waiting to happen. Try using dscaler from
www.dscaler.org instead. Also TV's native resolution is 320x248 or something close to that. If your trying to hook up your gamecube to your pc, make sure you use the svideo out instead of rca video if available. I hooked up my xbox to my tv tuner card via rca composite output and it looked pretty blurry and crappy. I bought the svideo cable for it and it looked a little better. I think in general, video games dont look too great on tv tuner cards.
btw I got my pinnacle pc card for 20 dollars after rebate at compusa....I wouldn't have gotten it otherwise if it hadn't been dirt cheap. Just look at their own website forum for an example...many many complaints.