MacBook – Problem booting from a DVD: How to eject the DVD

According to Apple documentation, you can either use eject and F12 as mentioned before, or keep your mouse button pressed.

If you keep option pressed during boot, it should ask you from what disk you want to boot. That might be a better solution.

Are you sure this is the issue though?

I think what you're trying to do is simply burn the contents of the ISO to a DVD, but what you need is a program like Disk Utility to copy the ISO bit by bit to the DVD maintaining its bootability. Try this:

• Open up Disk Utility.app in your /Applications/Utilites folder.

  

• Click "Burn" in the tool bar.

• Navigate to the ISO disk image you want to burn.

• Click burn to start the process or click the disclosure triangle to select further options for burning your disk. Faster write speeds are faster (d'uh) but make the operation more prone to failure due to vibration. I suggest you click the check box to verify the data of the disk once it's burned, then pick whether you want the disk to be ejected or mounted once the operation completed.