The model number you gave is for an A-Open motherboard, not Asus.
The motherboard voltage regulator does not support voltages below 1.8 or 1.85volts. If the cpu you installed is a slot 1 P3 coppermine you will have to change the detected voltage to 1.8 or 1.85 for it to boot.
This can be done by covering connectors with tape or bridgeing connectors with Rear window defogger repair paint and tape. It all depends on the default voltage of your cpu.
OK, you do what when it runs for a few seconds, plug it in? A lot of boards spin the fans for a moment when the power is first connected, but that won't make them start. To start them, you have do have the power switch connected to the jumpers on the board normally labled "PWR-BTN" or similar. And hit the silly Power button. Unless you have a bad power button.
I have done quite a bit of testing (and yes, I was aware that a switch was required), with a number of different components -ie 3 different PSU's , 3 different CPU's(a PII266, a Celeron 300, and a PIII550 - all working fine in their respective systems), 3 different sticks of Ram, 3 different video cards (2X AGP, and a PCI) - all with the same result.
I have tried all the combinations I can think of (including disconnecting all the peripherals progressively). the only thing that made any difference was removing the video card (it powers up, I get a post error (beep) for the missing video card, then it powers down again). Replacing the video card simply fixes the (video) post error (but I still don't get any video).....
I have had a troll throught the forum at the AOpen site and there appears to be a reasonable number of posts from users with similar problems. Now I'm wondering whether this may be an issue with this model board....
I'm having exactly the same problem with a Compaq pc (mobo is an Fic Az31 (Compaq OEM)). Many hours spent at Compaq's site yielded *lots* of posts from ppl with same problem, but no solution (except to replace the mobo). Hope you find a solution.