Video behind on audio when playing HD file

I have a number of mkv files encoded with x264 and 1 with avchd.
Nothing is needed to have the video get behind on the audio when playing them on my htpc.
I have an Asus M3N78-EMH HDMI, AMD Athlon 64 X2,BE-2350, 2GB 800MHz DDR2 memory.
I think the cpu is the bottleneck here, but i'm not sure.
Can anyone advise me on what component to replace?
An xtra videocard (I use the onboard now), faster cpu (which one to buy?), other motherboard?

Thanx,

Twan

It's your processor. 2.1ghz isn't enough to play heavy encoded x264 files. This is because most likely your processor is doing all the work, and not your integrated graphics. This isn't your hardware's fault, but rather the software you're using to play them.

I would first try a different player: http://mpc-hc.sourceforge.net/
Get the standalone player (be it 64 or 32 bits for your system). The standalone player has codecs built in, so you can see how well they work. The player uses DxVA hardware acceleration, but it doesn't work on all mkv's.

If that shows no result, I would upgrade the processor. Upgrading your graphics card won't make a difference as far as playing MKV's. Depending on your setup, you can either get the 2.9ghz 5800+ (65Watts), or 3.0ghz 6000+ (125Watts) if your PSU has the breathing room.

And I see the RAM being the important factor here. Being that is a dual core processor, it should be able to handle the codec properly even though it it a realtively slow processor for todays technology. I have one, almost the exact same processor with 4Gb RAM and I get no lags or sync issues at all.

And I see the RAM being the important factor here. Being that is a dual core processor, it should be able to handle the codec properly even though it it a realtively slow processor for todays technology. I have one, almost the exact same processor with 4Gb RAM and I get no lags or sync issues at all.

weird, on Vista-32 bit I never get close to using 2 gigs even while playing movies. On my 64-bit system I do though.