The flashing Orange indicates a hardware issue preventing the computer from starting.
The rear LEDs could provide more detail as seen here:
http://support.dell.com/support/edoc...g/problems.htm
Scroll down to:
Table 4. Back Panel Diagnostic LED Codes
Here is a thread that covers everything from bad PSU to bad Motherboard to bad USB port and so on:
http://www.randomfix.com/2007/04/19/...e-power-light/
If it were the motherboard you should see the leakage and corrosion as seen in that link.
Check the USB ports for shorted (touching) pins. There are 4 pins inside a USB port.
If all the above has not helped we can then troubleshoot by removing certain parts inside and then seeing the results we get.
Here is a general Google on the Dell flashing Orange power switch:
http://www.google.com/search?hl=en&n...g+orange+power