Computer stars up for maybe 2-3 sec, then shuts off for 1 repeatedly

[Einzbern]

I bought my PC from IBuyPower a little over 2 years ago, and have since added a new cooling system and an older harddrive I had.
PC specs-
CoolerMaster HAF 922 Gaming Case
i7 950 3.06 GHz CPU
Radeon 6870HD 1GB video card
6 gigs DDR3-1600 ram
Gigabyte GA-X58A-UD3R w/ 4x PCI-E 2.0 x16 mobo
700 watt PSU
80 GB Intel X25-M MLC SSD
1TB harddrive
250GB harddrive (one I added)
Creative Labs Sound Blaster Audigy SE soundcard
Win7 Home Premium 64bit
H80I cooling system

I Apologize if this is the wrong place to ask, but here's a backstory leading up to the problem.

Maybe a week ago my previous liquid cooling system (IBP-Z001 I think) failed on me. Ended up buying an H80I as a replacement, and I finally installed it last night in addition to an older 250GB harddrive. All seemed well, temps were good.

Come this morning, things are still fine except for my sound which worked fine the last night. After fiddling around for a few hours I finally manage to fix it. Unsure if it was windows updates or simply reseating the card.

All seems to be running perfectly, but maybe 20-30minutes after that while playing WoW, my PC suddenly shuts off, then proceeds to turn back on for 2-3 sec along with fans and lights on the mobo. It proceeds to do this until I cut power completely either through a switch on the back of my PC or pulling the cord completely.

I've tried removing my sound card, video card, all but 1 stick of ram, a different stick of ram in a different slot, removing the harddrive I added recently, and reseating the CPU. The constant shutting off/turning on still happens.

At this point, I'm at a loss for what to do so any help would be greatly appreciated.

 

[Solf]

If you can be certain that your other components are working, and knowing how custom builders save the most on PSU, I'd check that power supply.

 

[Einzbern]

As a slight update, I have this really old PC with a P4(to give an idea of how old it is). Ended up taking out the PSU and it seems to be a 250W (says DC OUTPUT:250W on the label). Not sure if I could use it to power my mobo, H80I, and maybe a single harddrive to test if my PSU is the part the failed.

The other option would be to maybe plug the 700W psu into the older PC. No idea if that would actually harm it though.

Opinions? or other suggestions?

 

[Einzbern]

Update.

Got the 700w into my old PC, and it seems to power up just fine. Didn't plug in a monitor to be sure, but it seemed to stay on without the power off/on cycle it did for my newer PC.


Two questions:
1.)If the CPU is completely 100% dead, will the PC still boot into BIOS? Or perhaps will it exhibit symptoms similar to my own, where it will just constantly power up and down? What if I try to start with no CPU at all?

2.)If the PSU is dying or dead, and possibly starts exhibiting symptoms like my own, does it still have the possibility to power an older system? One that would previously run on a 250W PSU? Or would it be expected to show the same symptoms?

Other than that, I have no idea where to go from here.

 

[burritobob]

Your PSU is probably busted, you may want to either get a new one if you have a warranty use it on that PSU. First you should use your OLD PSU to test to see if you don't get the power on/off cycle, see if it's stable. If this is true your going to have to use the older one or get a newer one.

 

[Einzbern]

That's what I was originally thinking as well. I had a few people advise using the 250W in my newer PC, so I decided to try the 700W in an older PC.

Plugged in the 700W, and it seems to work fine in the older PC. No power off/on cycling.