Can I enable Remote Disc on a computer that shipped with an optical drive?
I've had to do this on an iMac with a failed optical drive before.

From http://www.mactricksandtips.com/2009/09/enable-remote-disc-drive-sharing-on-any-mac.html: 

defaults write com.apple.NetworkBrowser EnableODiskBrowsing -bool true
defaults write com.apple.NetworkBrowser ODSSupported -bool true


... then reboot, and hopefully the option will then show up in Finder > Preferences > Sidebar.