Which card to buy just to watch video..not a gamer?

I want to watch HD movies,downloaded XVids, and collectors concerts. Also play stuff like Hulu and Youtube.

I have Dell Inspiron 531 Vista PC and also Sammy Plasma HDTV connected via DVI/HDMI cable, Revolution 5.1 sound card connected to A/V receiver via SPDIF.

I would prefer to have a small version of the video on my PC screen (and full screen on the Sammy plasma) and I used to be able to do this with an older ATI All in Wonder card and XP....but can't get it working now with either the ATI 2600XT or NVidia 9600GT.

It seems kludgy to have to drag the media player into the extended desktop and max it to play a movie. But is only way I've gotten this to work with either of these cards. Then if I want to watch Youtube, I reckon I'd have to drag their player over and max it out as well.

I'm just curious how most people watch downloaded video?

Could anyone recommend a decent card for me?

Thanks in advance.