Jerky Ingame / Flash Graphics DMA Mode

I've encountered a problem on my new computer. but first, the system is:

Processor x86 Family 15 Model 67 Stepping 3 AuthenticAMD ~3000 Mhz
OS Name Microsoft Windows XP Professional
Version 5.1.2600 Service Pack 3 Build 2600
RAM 2 GB DDR2 @ 800
Display Adapter XFX NVIDIA GeForce 8600 GT
HDD ST3250310SV SATA IDE
Directx 9.0 installed.
Kaspersky Anti-Virus 2009



The problem occurs when I run a (in my opinion) low-end game just to see how it handles. I put in NFS5 Porsche Unleashed. Now when I'm actually in the game, the display is smooth for about 10 seconds while driving and suddenly becomes slightly jerky for a similar period of 10 seconds. This smooth/jerky graphics alternate throughout the game.

It was more noticeable in another game 4x4 Revolution which is another old game which should ideally run perfectly well on the 8600 GT.

I also notice this alternate jerky/smooth running when I'm viewing flash animation online with exactly the same 10s smooth/10s jerky performance.

I saw some material about DMA on IDE drives but I'm not sure if it's related to this particular problem and I am not knowledgeable enough to try it out without assistance.

I have tried:
a) Re-installing the display drivers
b) Re-installing direct X
c) Lowering the display quality from 'Quality' to 'Performance'
d) Scanning for Viruses and Malware, none found.

Any comments/help would be appreciated.

 

Sounds to me like something in the background is hitting the hard drive.

Try turning off the real time scanning for Kaspersky. If you've got Windows Defender installed, shut that off, too. Also stop Automatic Updates. If you're running a BitTorrent client or other P2P software, shut that off too. Now try the games.

Only other thing that strikes me as a possibility is temperature, but it seems to regular and consistent to be that.

 

Thank you for the prompt reply. While I was away I reformatted in order to understand whether the source of the problem was application based.

The problem still persists even with only windows installed, no anti-virus, update disabled, etc.

I'm completely at a loss.

 

I'm beginning to think that the trouble lies with my PSU.