How to debug Detect Displays? Having trouble using an external monitor I have a MacBookPro (MacBookPro5,4) with the DVI output connection and I can't seem to get it to connect to my Dell Monitor.  I've tried using Detect displays and made sure the monitor is using the DVI input.  It says there's no power coming from the cable and enters power save.  Detect Displays does nothing.  Any ideas?
A few steps to try:

Try a different cable
Try a different screen
Try a different laptop/macbook 

If you get success with one of these then the problem probably lies with whatever you left out, after that you'll have to try combinations of the above.