Crash on cold boot

Hi there, about a month ago I decided to get myself a new rig. I ordered the parts online and put them together myself. At first everything worked fine, I got Windows 7 up and running and drivers were installed without error. Then I decided to try and overclock my i5 2500k, since I have little experience with overclocking in general I googled a little and read up on a few step-by-step tutorials on how to go about with this. I'm not sure wether or not it's something I've meddled with that caused this problem, but in the middle of clicking around in my BIOS my computer suddenly dies. On reboot it halts and crashes after a few seconds only to reboot again before it even gets to the initial boot screen. It keeps going like this for 3-4 consecutive crashes until I pull the power. I open up my case and since my motherboard has a "mem-ok!" button which, according to the manual is used to reset BIOS and allow a safe boot. I press and hold for 5 seconds and it boots correctly and lets me undo any changes I've done to the BIOS. Everything seemed to be in working order, but now whenever I do a cold boot it still halts and crashes once or twice before it does a succesful boot. The problem has persisted for a few weeks now and it's bugging me because it means there's a problem somewhere. I'm clueless as to where exactly, though. Anyone with experience or input that have ran into similar issues? Feel free to share your thoughts.

Oh, and if it helps I thought I'd add the full specs of my computer:
ASUS P8-Z68V
Intel Core i5 2500k
Corsair Vengeance DDR3 1600MHz 8GB CL9
MSI GeForce GTX 560Ti 1GB PhysX (Twin-Frozr II)
Corsair TX V2 750W PSU
Corsair SSD Force 3 120GB
Seagate Barracuda 7200.12 1TB

Thanks!
Thomas

Thanks for the reply and welcome. You're correct, I get no screen picture whatsoever, it just flat out crashes and reboots a few seconds after I hit the power button and does this at least once, sometimes twice, before it boots succesfully. And yes, this still happens when I shutdown/reboot after the computer has been on for a few hours, so I guess my topic is a little misleading. It's working perfectly in Windows so far, no BSOD or anything so I don't think it's a software related issue.

I will take your advice and check the connections, will post back if I find anything.

My experience may be helpful.

My new PC would work fine all day and could be shut down and rebooted without a problem. Except if shut down overnight. The next morning on booting up it would hang at various stages of the boot up or repeatably re-boot. After trying various actions such as repair or safe mode, it would eventually come good and work for the rest of he day.

I took it back several times to the seller who said that it tested OK. Nevertheless, he replaced parts until it had a new hard disk, motherboard and power supply but the problem persisted. There was not much left of the original computer.

Eventually, I downloaded memtest and created a bootable CD.

The first run of memtest showed no errors but when run from cold in the morning bingo! Up came a screenful of red messages. Ten minutes later the error messages stopped and the memory tested OK from then on.

A new RAM memory stick fixed the problem

You do realize this is a very old thread.