I have p7p55d e pro , I5 750 . 2X2 1333 KINGSTONE , GTX 470 .
I had to travel with my pc so I took it apart and I carried it in my hand bag to make sure it is safe . when I arrived , I re-installed it again .
Surprisingly , the mother board keeps rebooting for ever and no boot at all , no monitor data , nothing at all , just a short beep .
but the cpu led turns on (red ) just before it restarts , so I thought it's PSU problem (OCZ 600 ) so I bought GIGABYTE 720 , but still the same problem .
I have deleted the cmos using the deleting jumper to reset the bios and still the same problem .
I tried to reinstall my computer out side the case to make sure there is no short and still the same problem .
I have unplugged all cables from the mother board except for cpu able and mother board cable and cpu fan and turned the computer by activating power jumper , but the still the same problem .
I tried to run the system with only one ram , but still the same problem .
THE MOTHER BOARD DOESN'T RESTART ONLY WHEN I UNPLUG THE CPU CABLE , BUT OF COURSE NO BOOT OCCURS .
I noticed that the short beep occurs only when I connect the sata port but NO BEEPS at all when I disconnecet it .
Also , I have been overclocking to 3 (not much ) , is this a problem ?...I believe clearing CMOS should reset the default frequency .
It could be that you have mixed the original booting hard drive cable. I recently had this problem too and got it solved by simply switching the boot drive cable a couple time till the system booted well. I thought this couldn't happen on SATA, though... Hope this made any sense.