Computer wont boot up, help pls

Today my computer just suddenly closed itself. Now when I try to boot it up the power light just flashes and the cpu fan takes a few spins, then it just shuts down again. What could be the cause for this`?

My specs:
AMD Athlon 1400Mhz
256mb ddr
geforce4 mx440
250W power

Any beep codes?

No beep codes. I'm positive that the mb gets power since the led on it turns on when I switch the power on. The power supply also makes that sound it makes when it's on. Tried booting without a video card too (shouldn't it power up even without one?). I had this problem a few months ago too and one morning it just had disappeared, wierd.

It basically boots up for like a second or maybe only a fraction of a second and then it dies. Any suggestions?

Try a power supply, check all your connections. If you can, try sticking the cpu in another motherboard (a friends maybe).

had the same prob a few days ago putting together a new machine. reinstalled the processor (reversed the fan orientation actually) and now everything works.

if that doesn't work try replacing the power supply. if it still won't work, consider replacing the motherboard.

The problem was indeed the powersupply. It was badly burnt, 250W powersupply couldn't handle the last HD i inserted to the system. Also at the same time we noticed that the chipset fan and chassis fan were both broken. Replaced the fans and powersupply and now everything seems to run fine. I will also insert a new bigger chassis fan to the system since Thunderbirds are known to run at high temperatures.