Pc not start!

Take everything out of the case. Set motherboard on a cardboard box and only plug in basic components such as power supply, hard drive, and video card. Also install a minimal amount of RAM (1GB is fine). Then turn it on. If you do not know how to turn on a PC without a switch then take a screw driver and touch the two pins (at the same time) on the motherboard that is for power. Post the results.

that dose not work.

did you try shorting the pins?

yes
is it possible that the mother board can be broken cause i tryed to switch do an old motherboard and that worked?

It could be almost anything.

What are your system specifications?

but i have tryed to start the computer with only the cpu and cpu fan, and that did't work and i tryed to swith motherboard and that worked

do you mean the compnents?

It could be almost anything.

What are your system specifications?

I kindah sound like a idiot saying that, but sometimes its sometimes always simple.

did you apply the stand offs?

i had the exact same issue.
What i did, is on the back of the PSU, there is a switch. I have my switch set to the dash line, and not the circle. If i change it to the circle, I get a split second boot and the thing just turns off.

You might have already tried this, but oh well. Just a suggestion.

yes

1. Answer questions asked of you.
2. Read http://www.tomshardware.com/forum/261145-31-perform-ste...
3. Read http://www.tomshardware.com/forum/264823-31-progess-tro...

Also any post beeps, Make sure the video card is in good and has the power connector in good as well

i have cheked all that and i have a speaker on the computer and i dont hear any beep signals

I'll add a fourth request for you to list your complete system specs. Does it help if I say PLEASE? If you're not willing to answer questions asked of you we're not really going to be able to help.

I highly doubt you've actually performed every step in both of the linked troubleshooting guides. They were created to troubleshoot this exact type of problem, but you have to perform EVERY step in order for them to work. It seems like you may have already answered your own question, though. If a different motherboard solved the problem then it looks like your motherboard is faulty.

i have done performed every step

Yea, Id say RMA the one you bought or save up and buy another one. did you buy your parts from newegg?

no i bought all my parts from a local store

Well I'd go to them and see if you can return your products for some money back or new parts.
Also, like the people said above. What are your parts?

motherboard: GA-P55a-UD3
psu: saga ll 500
RAM: Kingston 8 gb
CPU: intel core i7-860
CPU cooler: stock
video card: gigabyte 8400 gs
Case: nexus version 1
Operating System : windows 7

Thanks.
You got some pretty good parts my friend.
But I would seriously try to see if you can return your motherboard.

i am but the computer dude from the store is on a vacation to next week soo i got to wait

It shouldn't matter whos at the store. Lol. As long as someone is working there

i know, i said that to them.

is it possible that some of tha parts not are compatible with eachother?

It's possible, but you haven't given us detailed enough specs to tell you for sure. What EXACT RAM kit do you have? "Kingson 8gb" doesn't give us enough information. We need the exact model number of your RAM. The max RAM voltage supported by Intel chips is 1.65v. Many Kingston kits require more voltage than that. That will cause stability issues, but not really cause the type of problem you're having.

What power supply do you have? A cheap PSU will also cause all sorts of issues.

Of course we're kind of wasting our time on this since you said the system worked with a different motherboard. If that's really the case then the problem is obviously your motherboard.

okey

I hope there is an issue with Power supplies..

There might be several reasons for this as given below:

1. SMPS may not be delivering the perfect voltages as designed...so the processor stops working as a preventive act.

2. The line on the mother board might be getting shorted.

So check by switching it on again and again by removing cables of mother board one for one time. This will help you in finding where the problem is existing.