Windows 7 - Computer simply won't power on

I just received my new computer parts today. Specs:

Core i5-2500K
Gigabyte P67X-UD3-B3 motherboard
Sapphire Radeon HD 6870
8 GB DDR3-1600 RAM

to go with my Corsair Force 2 120 GB SSD and 320 GB Seagate HDD. Now the only problem is, after I've connected everything, the computer simply won't power on. I have a Corsair 650W power supply so I'm PRETTY sure that shouldn't be an issue. I'm positive everything is connected to the board correctly so I'm at a loss. Any ideas?

Maybe take out the ram and graphics and reseat them?

Triple check all the power cables are plugged in correctly?

I assume the power supply was from your last rig so it was working fine in that?

wont power on as in?
wont post, or just does nothing when you hit the power button?

If it does nothing when you hit the power button, have you actually got power? is there a switch on the rear of the psu? flick it. is the power button itself at fault? try manually shorting the pins together with a screw driver.

if it does power on and you get fan spinning but nothing else, check your 4/8 pin pci-e power cable is plugged in.

do you have a speaker attached to the mobo? does it give a post beep?

when building a new pc ALWAYS build it outside of the case first, i do it on top of the mobo box, jsut plug everything in or the minimal needed to make a computer work and turn it on, by manually shorting the + and - pins together.

CMOS battery checked/replaced?

Newer PSUs are getting more and more finicky about supplying power if they feel that anything is wrong...

You will usually get an indication of this in that the cpu fan gets a power hit and moves a bit but then shuts off instantly.

Make sure that you have (besides the large power plug) the CPU power plug installed and the right one, could be 4 or 6 or possibly even 8 pins. Also that your GPU has all of it's "external" power connectors populated.

I solved the issue. There was something seated incorrectly on the board. As soon as I removed it, the computer was able to power on. Should've kept trying before I posted a thread. Thanks for the help though, guys.

You may want to read this useful guide: No Power to Computer - How To Troubleshoot a Computer That Shows No Sign of Power

When you put the case back together did you make sure everything was seated correctly?

I was troubleshooting a friends computer recently and it turned out that the front panel wasn't seated correctly, which meant the power switch wasn't being pushed in fully.

As this computer was self-built, did you double check everything was configured correctly?

Glad you got it sorted

You're welcome.

It's normally the simple things that cause this sort of problem and you could have have considered yourself unlucky if the new power supply had failed.

Thanks for the update.

Just to point out to a few that don't know this

First time builders may get this due to not grounding the board correctly to the case or configuring the ground screws in the right areas the board was designed for

In case someone has a issue that is also something to check for

When the motherboard is not seated properly it will attempt to turn on but fail

Just some extra info