I have a older Optiplex 755 when i plug a RGB cable in before it boots it has a green power button and 123 lit up. Green power button and 123 usally means a error. but a wiki says look for what is on the monitors when i have a cable in my graphics card to monitors there is nothing? This optiplex only does this when a RGB is plugged in  its not on the graphics card that wont work my card does not have RGB the only time the front LEDS are lit is when it powers on it flashes all the falt lights then boots