Counter-Strike: Source. Lag issues.

Hello, everyone! I'm having an issue with CS:S. It has nothing to do with my network, or in general my ping or anything to do with Internet. I get lag problems, like low FPS. It usually happens when moving, there is no lag while Idle. Anyone have this problem and have fixed, or know where/how to fix it? I've checked the other Topics about CS:S lag issues, but they all have something to do with the internet and their connection. I've updated my drivers (video and sound), that helped a little but there is still serious lag.

I played CS:S before installing Windows 7. I also reinstalled steam and CS:S.
Please helpz.

[Edit] Specs
Windows 7 RC, Build 7100. 32 bit
CPU: AMD Sempron 3100+ ~1.8GHz
RAM: 2gb
Video Card: Nvidia GeForce 7800 GS

~MrGreen.

I am having the same exact problem as you, with almost the same exact computer (but with a real mans processor). I was running WinXP last and getting 120 fps on CS:Source with maxed out settings. I did a fresh install of Windows 7 Professional and now CS runs at 12-15 FPS and is choppy as hell. I wonder if it is our video card drivers? I dont think the issue is RAM as 2gb should be plenty sufficient to run counterstrike for God's sake... its not Left4Dead 2 or anything....

And furthermore on a tangent, wtf is the deal with these new windows OS's requiring so much RAM? They build ****ty software that requires a ton of memory to drive up the market on RAM and require people to buy more and more. Ridiculous if you ask me. I wish Linux would step up their game and get something out for the masses because i just cant stand Apple and Windows is driving me mad too.

Specs:
Windows 7 Pro, build 7600 32bit
CPU: P4 2.80ghz with HyperThreading
RAM: 2gb DDR400
Video Card: Nvidia GeForce 7600 GS (512MB)

thanks DarkXeno. How do i make sure the pagefile is turned on? and is dx9.0c newer than directx11 because thats what i have installed... thanks again.

so if i download and install dx9c then it wont override my dx11? Do you think it could be a nvidia driver issue or no? I dont really want to upgrade my PC to play this game as its the only game i really have ever played.

Thanks alot DarkXeno, it worked. Although, i'm still only at 50fps now, its more manageable. I will try to find the drivers for Nvidia 189xx and see if that helps. It looks like i have 170.xx or something... but i just downloaded it so we'll see what happens.