The status light flashes and the computer won’t start up.
* If you recently installed additional memory, a PCI expansion card, or another internal
component, make sure that it is correctly installed and that it is compatible with your
computer. See if removing it allows the computer to start up.
* If the status light still flashes, determine the number of flashes to identify the
problem:
* 2 flashes: no RAM installed
* 3 flashes: incompatible RAM installed
* 4 flashes: no good DIMM banks
* 5 or 6 flashes: contact Apple or an Apple Authorized Service Provider