1080p playback issue

Hi,
Been having issues with jittery and out of sync playback of 1080p mkv's. I am currently running a AMD 4200+ with 2x 7600gt in SLI. Whilst playing the CPU load seems to be anywhere from 75% to 100%. Playback is on a 40inch 1080p LCD. My following questions are:
1. Running 169.75 (i think, there the latest nvidia drivers for the 7 series), do I try different drivers? If so doe sanyone have link to those (for vista 32bit).
2. I have not played or altered the defualt codec's aside from installing the combined community codec pack. Was this a bad idea? Are there alternatives that will fix this?
3. The 4200+ is a dual core that clocks at around 2.2GHz, does that need to be upgraded?
4. The 2 GPU's dont support oncard decoding of HD I believe. Am I better off removing those and replacing it with a nvidia 8600 or ati 2600 to utilise the onboard decoding and remove some of the cpu load?

Thanks in advance!

[Nety]

You could look at other codecs or maybe tweaking ffdshow. I tried CoreAVC which worked well for me however I would not give the company a dime of my money now as they are completely incompetent. (See my thread on that...)

I would look at replacing the 7600Gt's with a GF 8500GT or above however it will NOT help with MKV's in media centre as the hardware decoding does not work with them. However does work very well for almost everything else.

[ExtremePC]

My system plays mkv's smooth as silk and I run SLI 7950's. The only codecs I've installed are the latest FFDShow and latest Hali Media Splitter. Before you go changing any codecs as a test grab yourself the latest Media Player Classic, its an all on one executable so there is no need to install just download and open.

[Astrotoy7]

If you want an ultra lite footprint solution for mkv >> you cant go past Lazy Man MKV. Just a collection of the filters you actually need to make mkv work

The onboard decoding of the purevideo2 supported cards can be an advantage, but in some rigs not a necessaity

If I had to point a finger at a culprit from a hardware POV, it would be the 7600 on a 1080p display. Vistas DX9 SLI functionality is hardly optimised for gaming, let alone media apps.

But as in all things, when people have a mish mash of hardware, try all your software options first, drivers codecs etc, before you contemplate a new purchase... From a power consumption, POV at least, ditching an SLI setup would be a bonus for your power bill

good luck

astro