when I got a new power supply for my new graphics card. I plugged everything in on the new higher wattage power supply and then when I turned on my computer all I'd get was a blinking light on the power button (I didn't know it was amber, I'm color blind). It was kinda freaky too, because my computer didn't even have to be plugged in for it to keep blinking. Thats how I figured it had something to do with the reserve power supply. Its a little capacitor that stores energy even when the power is off and the computer is unplugged. Dell makes reference to it when they talk about holding in the power button for 3 seconds to "drain the reserve power" before installing any components.

Incidently, I did get that new power supply working. When my computer's power button just blinked, I'd push it in again and hold it for 3 seconds (all plugged into the wall and everything) and it was stop blinking. Then, I'd hit that button again the computer would boot normal.

In my case though, I didn't replace the motherboard and all that. I just put back in the old PSU because I didn't want the hassle. And the computer went back to normal. It works great even with the new graphics card, though the computer geek status quo out there has me worried about it being underpowered.