Hi, I built a computer in September of 2013. The following is a component list:
CPU: Intel i5 3350 3.1G 6M
MB: Asus P8Z77-V LX Z77 LGA1155
GPU: Gigabyte GV-R786OC-2GD HD7850
RAM: 4GB Corsair Vengeance DDR3 (2 of them for 8GB RAM)
PSU: Corsair 500W CX500
SSD: 32GB SDSSDRC-032G-G26 (holds Windows 7 OS + drivers + Google Chrome, that is it)
HDD: 500GB Western Digital Caviar Blue 5000ENC-NRSN (Holds everything else)
DVD Burner: LG GH24NS95
Case: NZXT (Black with blue LEDs)
All products were purchased from NewEgg.
When I go to turn on my computer, the LEDs light up, the fans spin up, the CPU fan spins up (it sounds like the computer is fully up and running) FOR ONE SECOND. Then, the power flashes off (as if the power cord has been yanked out), but after a 1 second pause, the computer starts up, POST beep sounds, and the computer runs fine. On the login screen, the compute doesn't even recognize that it was ever on (doesn't tell me 'Windows has been shut down improperly').
My amateur diagnosis is that the power supply is dying, but I really have no idea. I need help with this. Thanks everybody who contributes.