Hey there,

I've ran into this rather abnormal issue last week.
I've ran games, such as cod6: mw2, left4dead and devil may cry 4 mostly on mid~maxed settings flawlessly. However something snapped and all of the sudden I've started experiencing major lag in both cod:mw2 and left4dead.
(choppy sound, constant screen freezes)
However, despite the fact that dmc4 is obviously a next-gen game that requires alot more specs than left4dead, I can still run it flawlessly in 1680x1050 res "Super High" gfx setup.

Now all of this is rather confusing. I thought that maybe the issue would resolve itself upon reinstalling my OS, but even though I completely reformatted my system drive and moved from Vista to Win7, installing all of the up-to-date drivers, the issue is still there. I'm unable to run most mid-req games due to facing constant screen freezes, yet I can run devil may cry 4 all maxed out.

I checked temperature of both my gpu and cpu both of which vary from 40C to 45C even when running games. Considering that my gpu doesn't experience any problems running dmc4 on a maxed setup, I take it it's not a gpu related issue. The only thing that comes to my mind is the cpu, however considering that it doesn't experience overheating, that also puts me into confusion.

P.S. lowering graphic settings in any of those games doesn't show a slightest difference. The game lags/freezes just as much on the lowest performance setup as it does on the highest setup.
Yes I installed DirectX.
Yes I double checked all my drivers.
No, I don't have an abnormal amount of processes running in the background.
No, my ram isn't overloaded.

I'll try to post my pc details if needed, just tell me what app should I use to gather that info.

Thanks in advance.