ATI 4850.. slight constant lag in any game !help!

Hey guys.. I'm having this problem that I just can't figure out.

I play LOTRO , Battlefield 2, Demigod, COD4 & 5 .. all of them have a few frames lost every 1 second ... it's so annoying and I'm just about pullin my hair out on this one. Any suggestions appreciated.

I've: reinstalled latest drivers for vidcard, lan, audio, DX, disabled all bg running programs, disabled audio, reinstalled windows with just enough to run games, defragged hd's as well as check disk.. no errors

Specs:

CPU: AMD Phenom II X4 940 AM2
MB: Asus M4A79 Deluxe
Ram 4GB Patriot
HD: WD 1000GB SATA
Gfx: ATI Radeon 4850
PSU: Corsair TX750 watt
NIC Realtek RTL8168/8111 PCI-E Gigabit Ethernet NIC
Audio: Realtek High Def Audio

Win XP SP3

Any help is greatly appreciated

Almost sounds like the same thing i had when i only had 2gb of memory when playing Crysis. It'd stutter whenever it accessed the pagefile because i didn't have enough RAM. Although not quite as frequent as your problem.

How is you hardrive activity when you're playing games?

Check to see if your PC is recognizing all your RAM. You should also run memtest to determine if your ram is good or not.

Ok, Thanks for the recommendations ..

Still the problem persists..

I've dusted out the CPU and GPU heatsinks.. which was pretty caked with dust.. I dunno why I didn't do that beforehand.
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Reseated the ram, vid card.

I did download / install the CPU driver for XP at AMD's website upon new installation of xp.

Just to make sure heat isn't an issue.. I opened the case and put a utility fan pointing toward the hard drives just to cool everything.. so far running the game at CPU 31C and MB 27C .. not sure how to detect the GPU temp ... but I'm sure it's pretty low. Voltages +3.3=3.40 +5V=5.05 +12V=12.30... this is according to Asus PC Probe II

Thanks again for all your help.. any other recommendations?

Yea I ran 2 instances of memtest an it got to about 75% with no errors and I gotta run it again to cover the other 25% but Im betting I'll get thesame result as the other 75%.

Next thing I guess.. I will swap parts out with my bros comp and see what kinda result I get. Will get back later