New HTPC Build video quality issues 5750

Specs
XP 2002 SP3 non media center
Asus P5B dlx with E6400
2 gigs of Ram
ATI XFX 5750
Power Supply is Thermaltake 700W
Display Samsung Plasma HDTV HPS42 model

I think by searching I found a potential solution, but I have no clue so figured I would ask before buying anything else. Basically not gaming anymore and canablized my rig to make a HTPC for the kids and wife. My issue is video play back is balls. Its pixelated to some extent during movement. This is my first HTPC build. I went out and bought this card because my 8800gts 640mb didnt have hdmi out. Also I used a small case and needed a short card due to the case layout. I figured this thing would play awesome but I failed. It plays the same whether its a burned movie from the hard drive or right off the DVD player on the comp. Its sad when the 25.00 dvd player looks better then this thing.

This post by A-dub says that the card needs PowerDVD Ultra?
http://www.overclockers.com/forums/showpost.php?p=6296933&postcount=8

Will this hopefully fix my issue or is that just in reference to the bluray audio?

Any help appreciated.

It's just a reference for HD-Audio. What player are you using and what codecs to you have installed?

Well I was using windows media player, but now that you ask I am guessing thats probablly not the best idea. As for Codecs....... errrrr uh not sure I downloaded some, but not really sure which ones. Is there a place I can go to just get them all?
What player are you guys recommending? I intend to get a LG Blueray drive next month after payday.

Myself I like MPC-HC, only thing I download is AC3 filter, MadFlac, MPC-Video Decoder and Haali splitter.

Okay I dont know what I did wrong, but now I get sound but only a white screen . No video at all. Downloaded and installed the above itmes.