First and formost would like to say what a quality site this is and glad to be aboard.
Right my problem is modern warfare 2 (pc) (retail)
amd phenom 11 x4 925 2.8ghz
2gb ddr 2 800mhz
250gb sata hard drive 3.0gbs
700 watt thermaltake toughpower psu
Asus ATI Radeon 4890 1gb ddr5
Now i have a 16inch monitor so i always play everygame on 1024x748. When i play single player of modern warfare 2 my framerate goes from 120 - 20 fps when i going round the levels and back up. Some parts when gun fights are going and everything is blowing up the frames stay constant and smooth but in other areas for example favela level in act 1 the frames stay at 20-30 and its really choppy and annoying. I have latest ati catylst control and drivers and its bugging the hell out of me. I play crysis around 28-55 fps and its really smooth. iI have tried lowering all settings aswell.
I have tried reinstalling my operating system and all sorts but cannot figure out why it is not working properly.
Before i got the ati 4890 i had a xfx gts250 1gb ddr3 and mw2 used to run on all high settings and never hic up. It worked flawlessly but now im really struggling to play the game because the fps are so bad and 4890 is way more powerful then the gts250.
I have just put xp pro on my machine and im still getting the same problems. When running mw2 on xp or vista i still have 400-500mb free ram so that should not be a problem and with the gts 250 i had same system and it worked ok.
FYI, 400MB free is not nearly enough for games, which typically use all the 2GB Address Space avaliable to them these days. You definatlly have some form of RAM bottleneck, and would probably benifit from an extra 2GB of RAM.