My computer won't start up.  The power light on the front panel just blinks with an amber light.  I tried reseating all of the PCI cards and reseated the memory DIMMs and all other connections.  The system still will not power on.

From doing some research on the Internet and Dell forums this appears to be a common problem.

How can I determine if the power supply is bad or if the motherboard is fried?

The system has been in use for a little over 2 1/2 years.