A friend gave me his 23" Apple HD Cinema Display a couple days ago and it worked for awhile, and now it stopped displaying a picture.

I own a MacBook Pro and I have the display on my desk. I insert the DVI connector while my MBP is on and it goes into DUAL MONITOR mode, unfortunetly my external doesn't display a picture.

When I mirror the screens, I get the background I chose for the external on my MBP. I decided to disconnect everything and set it up on my kitchen table. When my external is not connected to my computer, I can't figure if the display even turns on. All I get is a random flashing of the white power light.

Is this a setting problem? Any updates for my machine? What should I do?

All input is appreciated.