Dead motherboard?

[hatesbluescreen]

How do you know if a motherboard is dead because I've had problems with my old computer were it kept on restarting after every 5 seconds.
The CD Drive was making the sound it usually does when I turn the computer on, it just did it every 5 seconds...
The monitor wouldn't even try to come onso I wouldn't even be able to get into BIOS. The lights on the keyboard and mouse wouldn't come on either.
I've already bought a new computer (it was time to get a new one anyways...) but I was just wondering what would cause a computer to restart every 5 seconds like that and what I should do if it ever happens again.

 

[raybay]

Except for the infernal eMachines, Packard Bell, and Sony desktops, It is actually quite rare for a motherboard to fail, unless you have been using it as a gamer, with a lot of resultant heat.
Motherboard failures at our shop, are actually one of these, in order: Bad memory, bad video graphics card, bad optical drive, bad power supply, bad cpu fan, bad thermal paste not allowing adequate cooling (this can be too much or too little thermal paste), bad cable, bad PCI component in a PCI slot (modem, sound card, usb card, firewire card, ethernet card). These should all be checked before you toss out the board...
If you have an eMachines, you can pretty much assume the board is bad, along with the power supply... which is also true of Packard Bell... and once in a while, the Sony.
The PCChips boards are also pretty fragile.
I would start by testing your power supply in another machine, or putting another power supply in your machine... then finding a way to test the memory in another machine if the power supply does not help.

 

[hatesbluescreen]

Thanks raybay!

I don't think it is PSU because I actually did test it in another computer which powered up fine.
I'm actually using the hard drive from the old computer in a new computer i built. I'll try all of those solutions when I get aother hard drive somehow.
I never throw away old computer parts so I still have the motherboard.