Is 2.4 quad core good or cor 2 pentium 2.6

Well if I am understanding the nature of your post you are asking if moving to an Intel® Core™ 2 Quad at 2.4GHz would perform better then the Intel Pentium 2.6GHz in a gaming system? The answer to your question is up to the game that you are running. So games are still not multi-threaded and as such they won't take advantage the extra threads that you pick up with the Intel Core 2 Quad. However if the application is multi-threaded for 3 or more threads the Intel Core 2 Quad will give you the better performance.

Now since this is a gaming system you need to understand that most of your performance is coming from the video card that you are using so you might not see much difference from one processor to another based on the video card you are using.

I would also adjust the amount of ram to utilise any dual/triple channel benefits you mobo may have
Moto

yes u right may br this is the fact i have got evga nvidea gt 520 card 1gb and ram 4 gb ddr2 800 and core 2 pentium 2.6.also my pc some time gets stuck for one second when i do multi like scanning removing program, download, browsing streammings in one time.i thought may its the fact bcoz when ever i see on cpu usage gadget its says always ram 50% and cores are most of the time quarter full and full .

Sorry, I read the Op which said 5Gb ram,  
but yes, full Cpu usage will cause stutter on any system
Moto

thanks
can iask you one more question .i installed smart defrager.i alfterward uninstalled it but its not going away from startup .its still working on statup .if i open it it still works.can u help me in that i also been in c drive in progrm files as well nothing there as well.
regard
saad

rightclick that icon and select uninstall, should work
Moto