Found this, hope it helps...
Disc images are a fairly common packaging standard for large software programs. If you want to try out a new Linux distribution, for example, chances are you'll need to download a disc image in ISO format and burn it to a blank CD-ROM or DVD.
But ever since I began using Mac OS X, I've been perpetually confused about how to burn ISO images. I'm used to disc burning utilities that have an obvious, explicit command like "Burn ISO Image to CD." To make life even more confusing, OS X's Disk Utility does have a Burn command, but it becomes disabled when you click on the blank disc you'd like to use for the burn.
http://hints.macworld.com/article.ph...60619181010389