Hi, I use to be able to play Modern Warfare 2 without any issues a long time ago. I had to uninstall it because I got bored of that game, and I re-installed it yesterday. For some reason I get lag spikes every now and then. Not teleportation lag, but FPS lags/stuttering. My fraps window tells me I am running it at 80-90FPS. When I get the lag spike fraps will drop down to 60FPS. This only happens in big maps, when I am in close range combat, or when I am nearby an enemy. I'm running on a 2.91Ghz Dual Core, 4GB RAM (+42.GB Readyboost), and an HD4870 512mb at 1920x1080 max settings. I can run very low resolutions fine, but my friends can run max settings (1680x1050/1920x1080) fine and their system specs are lower than mine. Why is it that I lag more than them when my system specs are better?
Could be a clock-rate issue. I hadn't played MW2 for quite a while until a couple days ago and I noticed the same effect. My screen would kinda "jitter" occasionally. But, I had also been testing a lot of various overclocking settings, including unlocking my 720 BE's 4th core. I decided to stick with 4 cores, but go with a known, 12-hour Prime95 stable clock of 17 x 200 @ 1.375v. The problem disappeared.
Check your CPU and GPU clock rates. See if reducing them just slightly gets rid of it.