WHAT THE HELL IS GOIN ON?

Your ram is running at 667mhz because it is running a 1:1 ratio with your CPU. Your CPU runs at 2.83ghz which looks like this

8.5 x 333 = 2830mhz or 2.83ghz
(multiplier) x (Base Clock)

Now the processors bus speed is 333mhz running quad pumped which gives you a FSB of 1333mhz. Your RAM will run at the same speed as the base clock in a 1:1 ratio which is 333mhz. You have DDR RAM stands for Double Data Rate so 333 x 2=667 so that is why your ram is running at 667mhz. You can go into bios and change the ratio to run it faster but it really does not effect the performance by much. The reason most people get the higher speed RAM is for overclocking stability when you start pushing the FSB higher and higher you need RAM that can handle it. When you see it say DDR2 1066 that is not the speed it will be running at that is just the max that it can run at.

Now as for your games restarting I dont have an answer you can try running MEMtest or Prime95 to check the stabity of your system but sometimes games justt crash I play Battlefield 2 and It has crashed a few times for no reason that I can think of it sometimes just happens.

dear SAAIELLO, thanks a lot about your quick and complete answer but i want to know is that a sofware error or a hardware one?

It could be either one without you providing an error code or message its hard to say which it is.

We have had quite a few posts and questions about pc's either restarting or crashing. There is a lot of speculation about pc components but the actual common denominator is that it happens while playing games. Of course that could be a coincidence because Tom's Hardware has a lot of members who are gamers.

Restarts are tough to figure out.

As i have seen it, Hardware errors are usually followed by a blue screen with an error code, and as of late, i hear that some 5xxx ATI cards are grey-screening but with no error code.

Software errors usually cause some sort of degradation in performance of screen freezing...

In one case i had a PC keep restarting on me due to a bad video card, but unless there is an error code or you can clearly see that the temps are way too high, it will be tough...

What are the temps of the video card and/or CPU?

gpu:50 c and cpu 60-62c (some seconds after a heavy game like evil5 or farcry2 or battlefield bad company2)

and one more question :what is cpu fan error(i havnt recieve that ) i just want ot know how it happens

If the CPU fan fails, the motherboard can let you know with some kind of a BIOS type beep. This feature can be enabled in the BIOS, usually in an area called PC Health.

what are the temps?
download speedfan to check them.

GPU:54- cpu1:45- cpu2:42-cpu3:45-cpu4:45- temp1:54-temp2:50_temp3:50-temp4:0-RPM:2150

So you are saying that your PC has restarted TWICE in the last year, and you are worried? Your temps seem OK.
If you really want to know if your PC is overheating then get ORTHOS, Furmark and CoreTemp. Run them all at the same time, and see what happens  

2 restarts in a whole year is nothing. I wouldnt worry, probably a software error. Fallout 3 and Crysis crash for me sometimes. Sometimes GTA4 freezes. Sometimes console games freeze. It's normal, think of all of the numbers flying around inside your PC's virtual mind when running a modern game. Sometimes things go wrong. Is almost inevitable.
I wouldnt panic about it, just save often!  

temps seem fine. Is it just restarts and no blue screens?

*** EDIT*** Oh man, i was under the impression that you experienced restarts all the time. If it only happened 2 times over the last year, i would say don't worry about it. It is uncommon but not out of this world... How long have you had that operating system installed?

14 month and i had no blue screen.

If you haven't done so, reset your RAM settings in the BIOS to match the settings printed on the RAM label. Then run the memtest86+ CD image at boot (about 1/2 down the page) - press the ESC key on POST to access the boot device (select CD). Many random re-boots are caused by unstable RAM, and it is always difficult to diagnose.
Let memtest86+ finish it passes, or shut it down if you get lots of errors, and adjust the FSB, RAM voltages and RAM dividers in BIOS until you get settings that result in the RAM passing memtest86+. When you are stable save the settings to CMOS Reloaded.

2 crashes a year sounds about normal to me.