HTPC Build - Questions - 4850

Hi all.

It is my time (again) to ask help from the people that roam this forums. If ever troll your post, i am sorry, but i would do it anyway.

Like the title says im build a all purpose computer (all done) consisting of:

Win Xp 32 SP2 (changing for Vista 64 SP1 in a near future)
AMD 4800+ X2 (stock, will possibly overclock)
Asus Triton 70 Cooler
Sapphire 4850 512mb (custom cooler)
Asus M2V
3GB DDR2
NZXT Lexa Classic (wife approved)
Corsair TX750

Of course i got some hdds and a dvd recorder to the mix, but this is hardly important. The problem is, while i can call myself tech savy, well, the Ms isn't. I want to keep it simple for her. A footnote on the sapphire 4850 (custom cooler). Very silent, good playback quality and while playing DVDs for my MS (on a 720p LCD) i can play my games without any stuttering from each sides. Excellent board. And in case of scaling for the TV Output is doing a dam fine job. I tested on several videos yesterday (DVD, Divx, 720,1080) and the GPU rocks.

First problem. 720p/1080p MKV movies. Anybody know a good player (or one that uses the GPU) for the decoding? Cyberlink doesn't read them and BS, GOM, Media player classic crap out on me. I don't if it is because of my (slow) discs or my CPU not handling the load. Hovering at 55% on both cores, and with frame skipping all around. Even only doing that, the image comes jerky as hell. Impossible to watch for over 5 minutes with the risk of ocular implosion and massive migraine. Any player you can recommend, knowing Cyberlink wont open it ?

Another point, is the 2 screen managing. The main user of this "HTPC" will be my Ms. Ive so far extended the screen, and configurated video to go over there. The problem is when opened, you need to "push" the opened file to the extended screen and them maximize there. Any CCC option i missed, or do you all recommend UltraMon ? I want to simplify it for ma Ms, so she will open a movie and it appears maximized the 720p LCD automatically, or the only way is to maximize on the extended screen ? Some overlay options on CCC didn't seem to work. I blame that on my X800 -> 4850 Upgrade. All works nice and dany, but some quirks were expected.

On the Vista/XP issue. I already did some testing and my little X2 behaves pretty well under 64bits. But from real life usage ? XP32 or Vista 64 ? It is a full purpose machine.

Thanks for the feedback once more. And feel free to troll my post It is the God complex, trolling the troll.