Sporatic laggy video playback from decent HTPC

[ChipMcC1]

First off thanks for all the help thats been afforded me here earlier.

I would like to correct/upgrade my system to avert lost frames from video playback which is noticable. It sometimes looks laggy when watching it. This can come from BD playback, plain DVD's, or even live cable TV. I have this HTPC set up with two screens. One is a Sony VW40 projector for watching and a Samsung 24" for playing games and surfing. It is more noticable while gaming and watching a DVD at the same time, but there are also times that only watching live cable TV will do it too but not as bad. Rebooting is the only solution so far.

Both monitors are being run thru a 9800 GTX, the Sony has a dual link DVI-D to HDMI and the Samsumg has dual link DVI-I. I know that running video shouldn't require much in the way of graphics processing so what could it be?
I thought about a second video card so that the video is on a discrete pathway but I'm not so sure that would solve it and thats just throwing money at the problem. This is a clean system with spyware/virus protection run weekly.. Any Ideas?

System = Vista on Intel G33 with Q6600 CPU, 4gb ddr2 800, 9800 GTX, Xonar X2, Happaugue Win TV1800, Seagate NCQ 750 gb, LG Combo drive BD/HD-DVD.

[minidv2dvd]

turn on the windows task manager. ctrl/alt/del - start task manager. make sure that the box "show processes from all users" is checked. on the processes tab double click on "cpu" to bring the highest users to the top. keep an eye on it and see what is stealing the cpu and causing the slowdowns. might be any number of auto-updating, auto-scanning, indexing programs. turn off all the "auto" functions you can. especially things like the anti-virus hard disc scans. do it all manually at your convenience.

not much should slow down your comp. errrr except maybe vista.

[ChipMcC1]

Thanks for your reply minidv2dvd.

I did try your suggestion and ran the task manager. I have aprx 70 tasks going and after prioritizing them I am not seeing any 'auto' ones. Also the cpu idle time is running in the mid 90%'s when only playing DVD and mid 70%'s while running a game + DVD. There is some stuff in there I don't need like a lightscribe task and DVD authoring stuff I don't use, but they were inactive during the 20mins I watched the task manager.

When I noticed this happening, my first thought was how do I increase the DVD playback buffer or increase the memory allocated to the DVD playback software. Is there a way to adjust these manually. Also, the other thing I like to blame stuff on is the use of virtual memory and the system using this when there is pleanty of RAM. Oh yeah, my RAM usage runs at 46%(with 4 gigs on vista 32 bit) and 55% with a game running.

Any other thoughts are greatly appreciated..

[minidv2dvd]

keep trying the task manager until you experience the stuttering and then while it's happening take note of what's at the top of the cpu list.

[ChipMcC1]

I haven't been able to detect anything in the task manager that may be causing the problem so far. I did check the BIOS to be certain the ACHI was set correctly for NCQ and noticed that the memory was being recognized at 667 Mhz instead of the expected 800 Mhz. I didn't get great memory when I built this for budget reason but am now thinking of upgrading it.

On that note I had a couple quick questions. What the deal with SLI ready/cetified memory? Is the any real difference or is that just marketing as I suspect. Also, is it better to have all the rails populated? Is 4 x 1gb going to be quicker than 2 x 2gb? I suspectt the later since latency should be lower with just two rails going. Just wanted another opinion..