I would remove the CPU and see if it powers up. The CPUs do a meltdown and this is a common problem.
Video on demand if you want to watch it.
I have an ASUS A7V8X-X with an AMD 1.4Gz that just zapped off while editing a document, and now it won't turn on. At first I thought it was a bad power supply so I replaced it with another from my kid's PC and still won't turn on. When powered up, the fan trys to kick start and then nothing. The little LED light inside the MB turns on with power. I disconneted the HD, CDs and Floppy so just the MB is powered and still nothing. The MB is just 2 months old.
Is the MB bad or could it be something else? Any suggestions?