The power light on my Dell flashes amber but doesn't start up. What does this indicate?

The computer is a XPS 420. I have changed the power supply, video board and hard drive. Since then it has worked for maybe a year. I had two monitors on the video card and about a month ago it wouldn't boot and when I disconnected the secondary monitor it booted up. I found Dell's troubleshooting guide online and in it there is information on the diagnostic lights. When I get home I thought I would look for these lights. I assume they are on the mother board.

I checked for diagnostic lights but found none. One of the suggestions for this symptom was that a fault bit might be set in the power supply and if I powered down, disconnected the power cord and pressed the power switch until all the power was discharged in the power supply capacitors that it might reset the fault bit. It works now. The on/off fan noise I described in my initial question is back so maybe it is the real cause and I need to fix it right away. When the cover was off I noticed the pulsating fan is on the video card. For now my computer is in the pink.