running virtual cd on a mac

Do you mean something like an .iso disk image? I don't know if it works directly in OS X, but you could try double clicking such a file to see if it appears on the desktop as a pseudo drive. It may open in Disk Utility, where you could save it out again as a .dmg (Disk Image) file. Those will mount on the desktop as a pseudo drive.

If your intent is to bypass copy protection on a purchased game that requires the disk to be in the CD/DVD drive before you can play, don't expect it to work. Almost all vendors of such games have changed the validation routines to see that the "disk" is actually being read from an optical drive. If not, it knows you're using an image and will refuse to run.