Cause - Bad External Power Supply
1. First be sure the External Power Supply is connected to both the PC and the electrical outlet.
2. Unplug the power supply from the electrical outlet, followed by the DC connection from the back of the PC.
3. Re-insert the DC-In connection to the PC and ensure it's connected properly, then re-connect power to the electrical outlet.
4. Now check the external AC adapter for a Green or Blue LED light .If there is an LED light lit up on the power brick, this indicates the power supply is functioning properly.
5. If the LED light on the power supply is not lit, then it may be bad.To verify, use a known working external power supply from another machine of the same model, if possible.
6. If the LED is lit but blinking, it may be a defective Hard Drive (see below).
Cause - CMOS could be corrupt
Refer to model specific instructions for clearing the CMOS.
Cause - Liquid Spill/Physical Damage/Internal Malfunction
Inspect the PC for any liquid spills that might have occurred. This could be any noticeable liquid or stains on the PC itself. Also check for any other evidence of physical damage/abuse. Check inside the unit for bulging or discolored capacitors or burned components. If a click-clicking sound can be heard when pressing the power button, open the unit and disconnect the power for the Hard Drive as well as its connection to the Motherboard. If the unit will now boot, the Hard Drive needs to be replaced.