I just put together this new computer.. haven't even put an OS in it yet.. I turn it on for the first time, fans and led lights go on for about 5-10 seconds then shuts off without anything showing up on the monitor. after it shuts off for about 5 secs and it does the same thing again.
Double checked all wiring and hardware components and tried it.. still the same...
I like dirtmountain's idea. 5 sec run, then shut down, sounds a lot like something heats up until a temperature limit is reached, then the BIOS is shutting everything off to protect it. And usually that's the CPU. A few seconds of running with very poor heat removal at the CPU will cause its temperature to reach critical levels.
Check CPU fan first - does it start and run immediately? Does it turn the correct direction? Check its connector to the mobo - is it plugged it correctly? Among other things, the BIOS will check the fan's speed signal coming back on the third wire - no speed signal and it will assume the fan is not turning and shut down.
Check mounting of the CPU heatsink. Does it appear centered over the CPU and lined up level with it - not tilted? Is it held down securely so it makes tight contact with the CPU? If anything looks wrong, you'll have to remove and re-do. But even if all looks good, proceed to removal. Checking beforehand simply tells you more about what to do next.
SHUT DOWN POWER AND DISCONNECT ALL POWER TO THE COMPUTER. Then start to remove the CPU and its heatsink / fan. Especially with a new install the heatsink should come off the CPU easily once its fasteners are loosened off. Be careful this way: Loosen, then remove the heatsink fastenings (screws, clamps, whatever) and GENTLY twist the heatsink a bit so that it turns free of the CPU, thus loosening the bond between the two. Now once it turns easily, you can lift it off, maybe with a slight tilt to one side to help it break free. Once it is off the CPU you can unclamp the CPU chip itself from its socket and remove it, too.
Check the CPU's socket. If any excess thermal paste got down into it, clean it off as best you can.
Examine the pattern of thermal paste on the heatsink and CPU mating surfaces. There should be a thin film covering the entire surface right to the edge, or almost. There should NOT be any bare contact area, nor any big squished-out paste along the edges. Look closely for possible lumps of foreign material that could have prevented even contact everywhere.
Remove all the old thermal paste from both surfaces. A tissue dampened with rubbing alcohol should do OK, maybe even several to be sure it's all cleaned off. Make sure not to spread any old paste over the edge and onto the contacts. Let the surfaces dry thoroughly.
Review the thermal paste maker's instructions again, and re-apply new paste. Sometimes people get enthusiastic and use the "more must be better" approach, applying a layer that's much too thick. Insert the CPU into its socket carefully, lock it down, then place the heatsink over it, centered. As you do this, a slight twist back and forth may help to spread the paste between the surfaces as pressure is applied. Fasten the heatsink into place. Sometimes (depends on the system) it is hard to do this uniformly. It seems llike you have to push really hard on one side and the whole thing wants to tilt, then it is almost impossible to get it straight again. Try as best you can not to have this happen by pushing the heatsink straight down on its center so that the fasteners on all sides can be connected. Before final tightening, make sure the heatsink is centered over the CPU and not tilted.
Im just going to stress how important it is to make sure absolutely no paste goes onto the socket/CPU
Its easier to avoid the problem than fix it... My Phenom was on the recieving end of my terrible cleaning, ZIF quickly became Alot of insertion force (especially since I bent several pins trying to clean it). If your extremmely lucky you just damage a couple of power pins (or none in my case), not lucky you can be happy spending a few hundred $s on a replacement.