When you mean by plugin, I guess you mean this. This Delegate Component will allow you to play XVID encoded movies in Quicktime player. To install, just follow directions on the site I gave you. However, if you want the actual codec itself, you can get if from here.Just download it and install. It should work then. Hope I could help.

P.S: This really belongs in Other Support but it's ok to mess up once in a while[img]i/expressions/face-icon-small-smile.gif[/img].