I put together a Core2Duo system about two months ago. It's been a great machine, but about a week or two ago I started to have issues with it. The system currently will not boot. If I tinker with it for a bit, I can sometimes get it to work for about 20 minutes before abruptly dying, but I figured to be safe and keep the system off.

Currently, if I try powering up the system, everything will start up for a second or two, then gets weird. The whole machine turns on, then off, then on, then off... the cycle repeats about once every second. It makes an audible click every time it does so.

I tried removing all components, leaving just the mobo, cpu and ram. Seems to work fine. Turned off and tried adding graphics card... no go. Removed power from that and tried hdd/dvd. No go. Anything above just the cpu/mobo/ram seems to result in the weird power cycle thingie.

Other weirdness:

I've had the system shut down while plugging in the headphone jack. Happened 2-3 times so far.

I've had the system lock up after extremely harsh gaming sessions (Crysis near max in extreme battles).



I've checked the system for possible shorts (things touching the mobo), but everything seems normal. PSU connections to mobo & components seem normal. CPU temp seems fine (~33C idle). GPU temp does not seem to be extreme(~42C idle).

Here are my specs (I'll put them in my sig later):
Intel E8400 Core2Duo Wolfdale 3.0 GHz
Gigabyte GA-EP45-UD3R
Corsair HX620W PSU
8GB (4x2GB) Crucial Ballistix Tracer DDR2 800
XFX GTX 260 Black Edition Core 216
Samsung F1 1TB HDD
LG 22x DVD
Antec Nine Hundred Case
Windows 7 RC1

Well your case seems extreme but once I had similar problem when reinstalling the OS enabled me to get it up and running. Try putting up a stable OS like XP/VISTA/UBUNTU and check if the problem persists.

Installing a new OS is not really an option, seeing as how the system won't start.

Sounds like the power supply

i would swap out the power supply with a new one..