playing HD videos on an old computer with HD 2600XT graphics card

[Gawwad]

hi

i have this ancient computer:
http://support.dell.com/support/edocs/systems/dim4500/specs.htm#1101572

cpu: p4 2.0 ghz
ram: 768 mb

and i have this graphics card on it:
http://www.ebuyer.com/product/134856

i am trying to make it play HD videos on my 1080p lcd tv

i heard that in order to use the UVD (http://en.wikipedia.org/wiki/UVD) of the graphics card, i have to use the latest version of PowerDVD

for some reasons, PowerDVD 8 Ultra was not activating the hardware acceleration of the graphics card on my computer (i did select it in the settings), but PowerDVD 7 Ultra did activate it

so using PowerDVD 7 Ultra i did manage to play a 1080p .mov videos (from apple HD trailers (http://www.apple.com/trailers/)) very smoothly, and the cpu usage was quite low

http://img169.imageshack.us/img169/2170/1080pmovep6.jpg

now i want to play .mkv HD videos on the computer, so i renamed the files to .mkv (as PowerDVD does not support the playback of videos with .mkv extension), but the problem is the playback was slightly jerky and no where as smooth as the playback of the apple trailers (.mov files)

note: the .mkv videos i tried to play were 720p and not 1080p as the apple trailers

i noticed that the less resolution .mkv videos required more computer resources than apple trailers on my computer

http://img396.imageshack.us/img396/6610/720pmkvcf0.jpg

so is there a problem with playing mkv files, that i can fix (so it play smoothly like apple trailers) or is mkv videos (with x264 codec) need more computer resources and there is nothing that i can do about it

will upgrading the ram from 768 mb to 1 gb (the max. my computer can use) will help in playing HD videos, or there will be hardly any noticeable improvement ?


thanks in advance
:thanks: