If you make a PNG image (editor: TIFF also works) with the RGB values 0,16,0 and set it as your desktop picture (the hint he saw recommended using a 1 pixel by 1 pixel PNG) then your DVD player can play on your desktop. Start a DVD and then hide the player!
This also works with the Terminal app. You can set your Terminal background to RGB values of 0,16,0 (with no transparency, unfortunately) and whatever the DVD player is showing will play through the background.
[Editor's note: This little trick will NOT work on NVidia cards; much as ATI's can't take screenshots, NVidia's can't play DVDs with the colored window trick.]

