after 3 hour watching cantonese movie online, I turn my computer off, but then when I turn it on again, it doesn't work. The yellow light of the monitor stay for 1s and turn to orange, and the CPU start running so loud like it gonna explode. Can I get any help here?

Have a look at this guide
Tutorial: No POST (Power On System Test)

It didn't work though, but thanks

What is your computers make and model?

read: http://www.techspot.com/vb/topic53866.html

I suspect your CPU fan is bad. Also check your PSU with a tester tool and multimeter.

Mine's Dell, I've just realized one thing that light on the power botton suppose to be yellow green before( when it's fine), since I can't turn it on anymore, the light is orange!!

What model of Dell?

Orange lights on the power button usually indicates a hardware failure of some sort, probably the power supply.

my CPU is GX 280. anyone know how did it happen?? I didn't do anything but just watch drama show online

Yes, a yellow light indicates an internal power problem or device malfunction. Try reseating your ram modules, check the power connections, and reseat the cpu, video card, and expansion cards. If you have another computer, you should try switching around all the compatible parts to see what is broken.

What you were doing before the PC failed in this case is mute. If you had been burning a dvd or editing photo's before you shut down the PC you would be blaming it on that I suppose. If a PC is about to fail then it will fail no matter what you were doing beforehand. Follow the suggestions you were given, if you have a Dell compatible powersupply you can swap with, try that.

Thanks for suggestions, but I'm not allow to open a CPU, I'm not professional one, so I'm not sure about that.

I don't burn anything on that computer, so...
and that computer I just got it last year, but I think it's old though ( someone already used)...

Do you still have the computer's manual? It has a troubleshooting guide, and a part replacement guide in it. It should explain how to replace or swap parts. And by no means takes a proffessional to do this. Good luck =). Oh yeah, and are there any lights in the back pannel that light up? On many dells, there are 4 LEDs on the back pannel of the motherboard, and they can give more detail about what is broken. You can find the light guide in your manual, or on the dell websight. Go to "product support" at the bottom of the dell page, and select your model, which is stated on the front panel.

Thanks for all replies, my uncle found out about the computer, he said the motherboard's dead. He handle it now