Media playback stuttering - DVD/TV Tuner

I have a fresh install of Vista Ultimate on my pc and I get less than
stellar performance when watching live TV via my ATI Wonder Elite
tuner card. The video stutters and is choppy. When I resize the
video window to its smallest size there is no stuttering.

I get the same choppy video when playing any DVD in full screen or
window in Cyberlink PowerDVD software.

My WEI score is 2.0 and that is based on my video card - nVidia
6200OC. Will a better video card fix my media playback issues?

Also, I have 2gb of ram (DDR-3200) installed but yet my WEI score is
only 2.5. Is this a bottleneck as well?

Any thoughts, tips or questions would be greatly appreciated.

Thanks,
Tom