How do I share an optical drive with Windows? I need to install something from a CD on my PC, but it doesn't have an optical drive.  I have an optical drive on my Mac.

I have enabled "DVD or CD Sharing" from System Preferences:Sharing.  However, when I browse to my Mac on the Network (e.g. \\OSXHostName I don't see the optical drive show up.)

If I add the drive as a shared folder, then I can see it under (e.g.) \\OSXHostName\OFFICE12 but when I double click on it, I get a dialog box telling me it "is not accessible. You might not have permssion to use this network resource..."  But in file sharing everyone has at least read-only access.

I did find one trick mentioned, whereby one creates a symlink from the mounted optical drive to one's home directory, e.g. ln -s /Volumes/OFFICE12 ~/OFFICE12.  But when I do that it doesn't show up (it seems to be hidden) and if I try to manually enter the path into Windows Explorer it says "This file does not have a program associated with it for performing this action..."

I have no problem accessing the home folder on my Mac.

All the instructions I seem to find mention sharing an optical disk on a Windows PC to a Mac, or sharing an optical disk from one Mac to another.  How do I share an optical disk from the Mac to Windows?  I expected it to "just work".
It would appear tubedogg is correct. Or at least I know of no reason he/she is wrong. HOWEVER, while you may not be able to share the optical drive, it does appear you can share the content (CD or DVD) in the drive. This means you must insert the disk into the optical drive before enabling the sharing of the content with the Windows machine. I have verified this for both a data DVD and music CD.

Setup with Empty Optical Drive on the Mac

The Finder shows the following. The Coelacanth and Marlin are the only visible internal drive partitions on the Mac named Marlin. 



Sharing under System Preferences shows the following. The only shared folders are each user's default public folder. The "File Sharing" box is checked off, as well as, all boxes in the "Options..." popup window. The "DVD or CD Sharing" box is not checked off. 



Note: "Screen Sharing" is only checked off, because the two computers are currently connected using VNC. I verified this has no effect on this answer.

On the Windows PC side, the machine named Shark displays the following. Here, the Mac is already sharing its folders with the Windows PC. The internal drive partitions "Linux HFS+ ESP" and "rEFInd" are flagged as hidden so they did not appear in the Finder window shown above.



Setup after Inserting a Data DVD Into the Optical Drive on the Mac

The DVD now appears in the Finder, as shown below.



I clicked the + symbol and added the DVD to the list of shared folders shown on the Sharing window of the System Preferences. The result is shown below.



This results in the DVD automatically appearing on the Windows machine, as shown below.



I can now open this folder and access the files on the DVD.