inexplicable gaming slowdowns

all right, so I've been having this problem with many of my games and my computer in general, and it is incredibly frustrating.

so here's what happen's, any game that i play that uses 3d graphics (be it anything from the witcher, to half life 2, to black and white 2) will slow down periodically at the most random of times.

It could be when I'm in a huge battle where there are plenty of effects or ragdolls flying around or it could be when im looking at a wall or floor or whatever. The point is no matter what I'm doing in-game the game will go from 40-60 frames per second to under 10.

I really need help with this. the only other information i can give u is that the slowdowns happen in 3-10 minutes intervals from about 10-20 seconds and at any given moment.
any help would be greatly appreciated, thanks.

here are my system specs (i built my pc from scratch):
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motherboard: m2n-mx se plus

video card : Nvidia GeForce 8600GT

OS: Windows XP Professional (5.1, Build 2600) Service Pack 3, v.5657

BIOS: BIOS Date: 03/26/08 10:37:53 Ver: 08.00.12

Processor: AMD Athlon(tm) 64 X2 Dual Core Processor 5000+, MMX, 3DNow (2 CPUs), ~2.6GHz

Memory: 4414MB

DirectX Version: DirectX 9.0c (4.09.0000.0904)
500 watt power supply
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edit: looks like i posted my thread in the wrong forum any1 know if i can change that somehow or if an admin can

 

try this first

http://www.amd.com/us-en/assets/content_type/utilities/DCO_1.1.4.zip

also check and make sure all the fans in your pc are dust free and in working order

Edit : running latest drivers ??

 

wow this little install really helped, thanks. its working perfectly now.

 

pfft typical AMD!

INTEL FTW!