Dell Graphics issue

I have got a dell computer that will only display video if the monitor is unplug when powering up the computer.

If I power up the computer with the monitor plugged in the monitor will light up and the power light will turn green however it only display a black screen. The computer will power up but the white light on the motherboard will not light up. I notice I can push the power and it immediately shut off. I don't have to wait for the hard drive to power down windows or have to hold down the button and wait for the computer to shut off.

If I unplug the vga cable from the computer and power up the computer the white light will come on and lights on the keyboard and mouse will light up. I can plug up the vga cable while everything is running and will get video.

Does anyone have a idea what the problem is?

 

i will give it a try. the monitor and vga cable works fine with another computer