Higher wattage power supply doesn't work while low does?

I just did an upgrade of my motherboard (A7N8X-E Deluxe), CPU (XP 3200+) and RAM (1 Gig in 2 sticks of 512MB 3200 DDR RAM) and because of the system specs I decided I needed to upgrade the power supply. I used to have a 300W, and I got a 420W Enlight. Stuck everything in, didn’t even post, no video, no drive accessing, etc. After a bunch of swapping of components, I finally discovered that it was the new power supply that was causing the problem, and that when I replaced it with old, under-powered supply, it started fine.

My question is, why would a newer, seemingly more powerful supply cause this problem? I tried it with both my old (Asus A7V) and new motherboard and the only thing that happened was that the motherboard light and CPU fans would turn on.

Because the new power supply is broken?

FWIW, I have run 300W power supplies on two machines, both with a hard drive, 2 optical drives, Athlon, and ATI 9600 card with 0 problems.

Don’t believe the power supply mafia. You don’t need to get surplus Pratt & Whitney parts, you just need a good quality power supply.

Can a broken PSU still output power to turn the CPU fans on?

Can a broken PSU still output power to turn the CPU fans on?[/quote]

A half broken one sure can. CPU fans run off 12V, while the CPUs usually run off 5V.