[la_z_boy]

I recently got Call of Duty: World at War and played through the whole game fine. Then a couple days ago I decided to play through it again, and found that all of a sudden when there's a lot going on screen, the game doesn't so much as slow down, but becomes very jerky, all the character animation will stutter constantly, it's like watching a movie in slow motion, but instead of a fluid slow-motion, it will go fast - slow - fast - slow, and the whole thing is instensley annoying.

I've also noticed that during the cut scenes while the level is loading, the cinematics and voice-over are incredibly stuttery and choppy, with the sound skipping in 1 second intervals (e.g. "our mission is...so that we will...brave men...on the island..." etc). This used NOT to happen.

Here is a basic rundown of my PC specs:
Processor: Intel® Pentium® D CPU 3.40GHz
The Motherboard: MSI MS-7173
Total RAM: 2047 MB
Used Memory: 923 MB
Memory usage: 45%
On-board Sound: Realtek HD Audio
Graphics Card: ATI Radeon X1950 GT 256mb

I have tried the latest graphics card drivers and older ones, and have tried to install the latest and much older HD Audio drivers; the problem still persists. I also have the November update for Direct X. I have also experimented with trying to delete all and any audio/video codec packs. I have also made the pagefile a lot bigger than it was...maybe that is a bad thing? Some forums say the bigger your pagefile, the better your games will run...

The whole thing kind of started with Dead Space. That was extremely stuttery until I read a forum saying it was a sound issue and so I updated and tinkered with sound drivers and hardware acceleration in dxdiag and it got rid of a lot of stuttering, but now I'm noticing that my games as a whole have started running more slowly and stuttering more than they used to. I also have Far Cry 2 which has lag that gets progressively worse until the framrates are unplayable... All in all a messed up machine!

Sorry to post such a long and complex story, but if anyone has any helpful ideas they will be greatly appreciated!!!
Raph