I just finish builting my computer couple of hour ago computer

spec are-
q6600 go stepping -thermalright 120 extreme with S FLEX 120mm fan
P35 Ga DS3P mobo
2 gig of ram
500GB hd
pc power cooling 750 watt psu
ati 1950 pro
TT armour 8000 case

When i press start button it stays for 2 second on then it shut downs automactic and turns it back on for 2 second and shut down again.

I look at cpu fan its not moving, I plug in cpu fan to another connecter the fan works but same thing shutdowns in 2 second. what could be the problem?

The fan not moving is likely due to a thermal monitor that turns the fan on only when needed.

As for the computer turning off and on.....It's time to do the usuall trouble shooting process. Unplug everything but the bare essentials, and see if it boots. If not, remove the mobo from the case and see if it boots on cardboard.

http://www.tomshardware.com/forum/ [...] -boot-help

this guy had same problem as me compter turning it on and off he says its a overclocking safey features? whats that i dont get any beep though.

Do what I told you, and you'll figure out the problem. Troubleshooting computers is easy...it's not like we're talking medicine here.

No, he's talking about the CPU cooler fan, which should always be on.

For the OP: One possibility for your problem: some MBs have a safety feature that monitors the speed of the fan plugged into the CPUFAN header and shuts down the system automatically if the RPM detected there is not "fast enough". By default, it is setup for the OEM Intel CPU cooler; some aftermarket coolers with larger diameter fans don't spin as quickly and thus may make this feature think the CPU cooler is not working properly. The feature can normally be adjusted/inactivated in the BIOS, but you may need to connect a faster-turning fan to the CPUFAN header temporarily to "fool" the system.

try hooking up the 4 or 8 pin atx to your mobo!

I had several machines with the same problem:
- some were due to fried mobos, even when right out of their package,
- others were due to failing PSUs.
Eliminate the second by switching PSU; if not, swap the mobo.

To dragonsprayer: LOL! That's a VERY good thought. I didn't think of that one myself. I know it seems really dumb, but everyone forgets the simple stuff sometimes.

To mondoman: Your post makes logical sense, but at the same time, I have to wonder what crappy company would be THIS limiting? Sell you a MB that protects you from breaking the CPU(like the MB company really cares THAT much about YOUR CPU) and at the same time can screw a customer that bought a tray CPU and aftermarket fan and their MB doesn't work. If I tried swapping out all the other parts I had spares of and realized it was the MB, I'd RMA it. When I got the new motherboard with the same problem, I'd change companies and swear that company X sells really crappy parts. What I would expect is maybe a reboot when the CPU hits the BIOS temperature threshhold or an error message when the computer is POSTing. I just can't imagine a company would be so bad to do that to their customers. Let's not talk about water cooling either.

Joefriday is possibly right that the thermal monitor turns the fan on only when needed, but it could also be a sign of whatever the problem is(bad MB?)

I would try stripping the computer to minimum to POST the machine and see what happens. Also check your 4 or 8 pin power cable and make sure it is connected.

I'm well aware of what he's talking about. The CPU fan will not always spin on certain mobos. I believe the DS3 is one of them.

i took out the cpu and heaksink from the mother and click start button it was running fine without restart like normal what could be the problem?

You mean it's running without a CPU?

yeah just notice thermalright 120 extreme might be touching the mother board heatsink to close together maybe

First time I've ever heard of a mobo booting w/out a cpu...

yeah there was no screen on my monitor or anything but without cpu and heatsink mobo was running.

Running without a CPU..........................?

Screw the Intel AMD war......Sounds like theyre both going to be out of business soon.

i mean to say system doesnt turn after i took out the cpu and heaksink but after reinstalled the cpu and heatsink it keep restarting every 2 second