Games Suddenly Started Lagging

Hello,
Later i started a new thread about my pc not turning it on. i got it checked and it seemed like the motherboard was burnt, so i had to replace it with a 'used' Intel quad core 2. The games before i got it replaced were lagging horribly , the fps just would fall suddenly. after replacement the games started working well but however 3 days later [4th day now] the games once again have suddenly started lagging suddenly with fps drops. and i had no problem with it 1 day before :/ ! What is the problem... do i require a re install of windows or what ?
My Specs are :
Processor : Intel Core 2 Quad CPU Q9400 @2.***** 2.66 GHz -2GB
Ram : Corsair 4 GB
System : 32-Bit System Windows 7
Graphics Card : Nvidia GT9600

Now dont say the specs are too low... because like 1 year before this problem started the games worked very nicely... infact i played crisis 2 on fps of 40 on this pc! and until now this problem seemed to be temporarily solved for 3 days. it lags 10 secs and goes fine 10 secs. its still less bad than last time but not bearable. The games i play on this system are mainly 4 games :
Dota 2
Planetside 2
Hawx
Minecraft

What i have tried :
1.Downloading Anti Viruses trials and downloading tune up utilities.
2.Cleaning up disk spaces and all.
3.Update all drivers.
4.Change Nvidia Settings and other settings.
5.And Until now when my pc stopped working... replacing the processor with the same type but that works and is 'used' because it dosent come anymore because of iSeries.
which has only fixed problem temporarily.

Thanks

Edit:
http://tinypic.com/r/12528pj/8
This is the software that i used and these are the temperatures in both Celsius and Fahrenheit of my pc stuff. This is while my pc is idle. ( no games , no applications but this software and only the browser ofcourse opened. )

Well yes, you should see if this is a software related problem first, and a fresh installation of windows could not hurt. You could also check for overheating, but that usually does not cause frame drops in intervals. If it is not an software issue, and you replaced the motherboard, processor and the graphics card, at least you do not have much hardware left to test

By the way, how much FPS are you getting in Planetside 2?

sounds like a software related problem to me.

Formatted my PC i also see everyone lag now on my screen except for myself. Also if I spectate someone, he will move normally but everything else will lag the same way they lag from my PoV.

Sorry about a mistake ... i didn't mean graphics card... only processor and motherboard. Anyways heres a bit more details. i was checking out steam for cool free games ( low on money, saving up for a system , till next year ) , and i checked out this game "Hawken" , i started downloading it, by the time it was done , i started it and suddenly things started to seem laggy, i quickly uninstalled hawken seeing it as a bad sign ( no offense to hawken fans, it just wouldent work for me correct ). and thats where it started. FPS on planetside 2 is buttery smooth on medium settings however when i interact with alot of players in a "region" , the fps can go as low as 30 fps. Can motherboards actually cause fps drops also ?

It actually seemed like that to me first also... but while running games i can find no software that is taking alot of power... all applications are like below 35000 and my games are the only thing above 200000. i have as i said downloaded anti viruses and stuff like tune up. i have uninstalled alot of unnesscary applications however to no luck at all.