I posted this on another thread and was given the advice to ask my question here instead:
I recently acquired a free desktop computer from a friend. He couldn't get it to work, gave to me, and he bought a new one.
Anyway, When first plugging in the PSU, and before i push the power button, the computer begins to boot up by itself. The lights, Hard drive, fans, etc will operate for approx 10 seconds (timed it with stopwatch) and then will completely reboot. Nothing appears on the screen at this time. No bios options, no motherboard splash screen. Nothing. This will repeat over and over if i let it (i couldn't handle more than 5 minutes for fear of further damage.
Here is the kicker, at ANY point during this boot loop, if I press the RESET button on the front, it will exit the boot loop, and boot up like there was absolutely nothing wrong. I let it say on for 4 hours, operated just fine.
Once i go to power down (throught the start menu, SHUT DOWN), it will power down just great. BUT, 3 seconds after being powered down, it will try to boot itself again and begin the boot loop cycle.
I have updated the BIOS to the most recent via a thumb drive and that was successful. The default settings are chosen and I verified that the setting for booting after power down is off in the bios.
I have tried with 2 sticks of ram, 1 stick, and 0 sticks. I have unhooked the CD/DVD drive from the PSU. Tried only running HD, MOBO, and PSU but still a boot loop scenario when plugging in. I even tried a spare PSU I had on hand with nothing different.
MOBO is an ASUS DQ45CB running Win7 Pro. 4gb ram, 500gb HD, and on board sound.
I tried to let it run all night once i was able to get to windows, but I woke up in the morning to a computer again doing a boot loop.
I read many other forums but none seemed to have my special case. Either they couldnt get past boot loop, or it was the CMOS battery or something. My battery is new, and have ruled out, ram, psu, HD, and power button on the front.