To supplement narins'
post, here is the Dell OptiPlex GX620
User's Guide (PDF): http://www.google.com/url?sa=t&rct=j&q=inspiron%20620%20light%20codes&source=web&cd=2&sqi=2&ved=0CGwQFjAB&url=http%3A%2F%2Fsupport.dell.com%2Fsupport%2Fedocs%2Fsystems%2Fopgx620%2Fen%2Fug%2Fpdf%2FN8071bk03.pdf&ei=GezhT5TcLqXl0gHY06HzAw&usg=AFQjCNH6y0NFzQK
Page 26:power light
The power light illuminates and blinks or remains solid to indicate different operating modes:
No light The computer is turned off.
Steady green The computer is in a normal operating state.
Blinking green The computer is in a power-saving mode.
Blinking or solid amber See "Power Problems." (page 291)
To exit from a power-saving mode, press the power button or use the keyboard or the mouse if it is configured as a wake device in the Windows Device Manager. For more information about sleep modes and exiting from a power-saving mode, see "Power
See "Diagnostic Lights
" (page 317) for a description of light codes that can help you troubleshoot problems with your computerPower Problems
IF THE POWER LIGHT IS BLINKING AMBER The computer is receiving electrical power, but an internal power problem might exist.
Ensure that the voltage selection switch is set to match the AC power at your location (if applicable).
Ensure that the processor power cable is securely connected to the system board.