My friend's computer won't boot and I figured that the power supply is bad. I thought this also because when I pressed the power button on the computer, I could hear the power supply struggling but not powering the computer.

I have a power supply (a 450watt one) from another computer that I know works that I installed in the computer that won't boot, and it still won't boot, but the hard drive starts spinning as soon as I flip the switch on the power supply.

I'm just making sure that the power supplies are compatible and that my friend's brother's motherboard is really dead and that it is not a power supply issue.

Thanks!

well most of the time if the power supply is bad the computer (fans, harddrives, cd-roms etc.) wont make any movement / noise.

if you can hear the computer start up, but no display, try removing the modem card if he has one. if that doesnt work try removing any other pci cards that might be installed (except if he runs a video card).

if there is still no luck after that, i would guess ram.

but as far as a computer running with a bad power supply.... only a power supply tester can find out. you can normally pick one up at a local computer shop (not a large retail such as best buy or circuit city from what i know) for about 10 bucks.

hope that helps

DO remove and clean the contacts of the video card (if not onboard), as well as the RAM modules. Reset them and check if it works.

good idea.. i've used the end of a pencil eraser to clean contacts before

Thanks!

I've used compressed air to clean all of the contacts on the power supply and RAM and even tried replacing the RAM, but the computer still won't power up.

I have also tried taking out all of the PCI cards (video is onboard)

None of the fans in the computer start, but when I hit the power button, I hear a buzzing noise in the power supply itself.

When I replace the OEM power supply with the heavy-duty one that I pulled from a working computer, the hard drive turns on when I turn on the computer, but the fan over the CPU doesn't go on, and no video is displayed.

One strange thing is that as soon as I flip the switch on the back of the power supply (the heavy duty one), the fans in it turn on.

Any other suggestions?

Thanks!

Sounds to me like the power supply blew and took the motherboard with it. Though, that's just hypothesis... you'd have to do more testing to find out the real story.

Would this be a good power supply tester:
http://www.google.com/products/catalog?q=p...1&ct=result