I just built my rig 3 months ago, and ran amazingly and cool. Had no signs of any troubles at all, ran very smooth like it should. Recently i was chatting on xfire and it turned off... I turn it back on and its running, Loading Windows XP screen and thats as far as i can get and it turns off again. The longer i give it a break the further it gets but never passes the win. loading screen. I tryed starting it in safe mode with networking and same thing happends. I even tryed to reformatt but it turns off when its about to. BIOS isnt a problem it doesnt turn off when its in BIOS. I never had this happen before, im guessing i got a lemon powersupply?  
 
PC SPECS:  
Antec Nine Hundred Case  
8800gts Superclocked 640mb  
Gigabyte ultra durable motherboard  
Corsair 620watt power supply  
2 gigs ram  
Quadcore CPU
 
 
O yea if it matters for the past week i let my PC hybernate so i didnt have to keep starting it up, would that cause this?  
 
Thank you all for your help, im am so sad.

im thinking its probably the psu. or the any system errors. what psu do you have??
 
and if it is any system errors, i would reinstall the windows.
by the way, why do you have windows 2000???......

I tryed to reformatt, and it just tuns off. no system errors.

Did your CPU fan stop spinning?    I know it's a silly question, but you didn't mention checking to see if the fans were spinning.  Aside from that, yes, I would agree that it's a faulty power supply.  

Yea i checked my fans, no question is silly. So i guss i need a better powersupply or use my warrenty if its still valid.

sounds like a power supply to me.. but that one should be fine.. I got the 520 and it's had no issues at all... I don't have those power needs though
Athlon X2 4600+ EE
MSI 580X
GeIL Black Dragon 2X1GB DDR2 800
WD3200AAJS
HIS X1950PRO (590/770)
Corsai HX520

Could be PSU, or your HSF may have un-installed itself.  I'd check the HSF installation, making sure all 4 pins are secure, cause it prolly wouldn't take long for the thermal trip to shut the PC off if it reaches the threshold temp.

Blackra1n, i think it may be a power supply prob. also but your right my power supply shouldnt be acting that way it's capable of handling all that power. and nice rig btw
 
GRIMMY! im going to try what you suggested and if that works, you will just be simply, the man, im sorry.

Sorry for posting again but i didnt check the HSF yet but i just realised, GRIMMY u were saying "..it prolly wouldn't take long for the thermal trip to shut the PC off if it reaches the threshold temp."  and i was thinking be4 my PC was on life support, i have that program called SpeedFan which if you dont know, tells you the tempature of everything. It would alert you if anything got too hot. Maby it just shut off too fast for it to warn me but i dont know. Also its wered that u said it wont take too long b/c it shuts off at the same time which proves your statement. It once brought me to the black screen saying that my PC wasnt "shut down properly.. and i can start it in safe mode..". it gives me 20 sec. to make a decision and if i dont it's off and the end of the contdown.

One quick test you could try, laid the system on it side, to where you can push down on the  center of the fan, so you can evenly put pressure on the HS, and see how far it will boot.

The countdown will resume to the default selection, which should be run windows normally.

Edit:

Is it the stock HSF?

That PSU should be BY FAR enough, however, it may be junk parts that can't hold it, albeit I doubt it, corsair being great mem..?
 
Unplug the power switch after turning your system on, they can get stuck...

Ok
 
Make sure that the cpu fan is correctly installed
 
if one pin doesnt not click in to place 100% the pc will shut down for over heating / chip protection
 
 
Remove board from machine
test each pin on each corner of the heat sink is fully in place
 
( youll see the black lug between the white pins on all of them - if one is missing thats your answer - remove it and try again - each pin must click at least one if not 2 - or even three times to get it in to place )   its a bit of an art but once youve done it you wont make the mistake again...
 
 
Do check this as it will save you money if it works

I tryed running in safe mode, still turnes off. NewEgg wont replace it with out the UPC code on the box b/c i cut it off to get the rebate, so now i have to go through the Corsair Company. I dont want a replacement i want to see if the'll put the money towards the 700watt one. Is that a good idea guys im so sad. COD4 im craving it!!!

On this one forum sumone said this "Try resetting your CMOS, it may have been altered. I had a similar issue, but i was able to get around it." i dont understand

yes stock HSF

Take off the stock HSF and clean off all thermal paste.  Reapply new thermal paste and re attach HSF... That would be the first thing I tried.  Also, try starting with only one stick of ram.  Re seat video card.  Sounds like SOME connection became undone

Have you tried running the unit without the hard drive at all?
If you remove the drive, let it boot up and sit at the bios screen a while but doesn't shut down it's probably a screwed up drive, or one of the memory dimms.
 
Power or heat doesn't seem likely out of the blue, unless you OC'd it.
Even then, just try it w/o the hdd at all.

 
 
k leme try that

 
No, ill try it without it.
The funny thing is i bought the Drive on Newegg and it didnt come in a box it was in this clear blue thing, its a Seagate Barracuda 250 gig. ill get back to u and see if that worked

WOW i was looking through BIOS with the Hard drive unplugged, and it didnt turn off. Then i did Xpress recovery and it didnt seem to do anything and it went fast. Now its working, im so confused, maby it just needed a nice massage.