Computer Turns off by itself

[d]

I put together a desktop from parts purchased today.. a P4 dual core 3.0 ghz, an MSI motherboard.. 1 gig ram.. and a PCI-E 8600GT video card. the trouble is.. when i boot it up.. it turns on, after a few seconds, turns off, and then turns on by itself again.. but there's no display. keyboard lights flash and everything.. cpu fan, gpu fan, everything spins.. but apart from that nothing.

There's this another PC i put together a few days back.. same proc, with micro-atx ASUS motherboard with onboard video.. it worked awesomely for a couple of days.. and now it won't turn on.. when i turn on, turns on for a bit and then shuts off.. two seconds it runs.. and then shuts off.. then it doesn't respond.. you've to unplug the power from the SMPS and plug it back again for it to even spin for the two seconds.. but after it turns off also the motherboard LED glows.. i've no idea what's going on.. i've tried everything literally..

 

[shantanu]

have you tried to check thats the parts are assembled correclty.. and whether you SMPS is ok.. try another SMPS with higher wattage...

 

[d]

try another SMPS with higher wattage...

I don't know.. i'm running a 350W SMPS on both computers... and one of those online calculator things show i need ~280W... so unless the quality of the SMPS itself is a prob..

 

[shantanu]

a fact : you can read you manual too , now a dayz atleast a 400w PSu is must.. and you are using a 350 watt and your Comp. demands at least 280 watts..

lets make it clear : the SMPS these 350 watts are and so arent True power, they give max to max 5A or 6A on a 12V rail.. and it cannot get your system up and running.. i am sure and that too with a 8600GT naah not possible.. just get a 400 or 450 watt PSu and your comp will boot up.. i am sure now

 

[Gigacore]

+1 for shantanu's suggestion