1. Bad brand new powersupply right out of the box...tried another one and it worked fine.
2. The fact that the cpu and fans start up for a short period of time sometimes and then quits immediately is indicative of over heating and the system shuts down to protect the cpu from burning up....check your thermal paste and heat sink fan mounting.
3. This is was a weird one on only one brand of motherboard and doesn't sound like your problem....the CMOS jumpers were placed incorrectly by default to OFF by the factory. The system wouldn't boot up at all until it was noticed and jumpered properly.
hey again, thanks for prompt previous responses.
Heres the deal - as i mentioned before my parts arrived just today from newegg(CPU AMD64 3ooo+, 512ddr rosewell pc3200, Chaintech ULi S1689 motherboard,chaintech geforce 5200fx agp256ram,case ASIAPRO|DT807T black 450W on the box its called ASYS ) and i've been trying to start the system all day without results. I cant even get the leds up working. Checked the manual connected the wires(power switch, hdd switch,reset switch..).I have installed cpu &ram, dont want to bother with hdd yet and when i tried to boot the pc nothing happens except that sometimes power supply and cpu fan start to work for 2-3 s and when stop. Anyone??