Either that Alcohol program or else Daemon's Tools. Some emulator and virtualizer programs such as DOSbox have a built-in function to mount an ISO as a CD-ROM drive.

There is only one thing I never could find a workaround for, and that's CD-ROM games that have music stored as actual tracks on the CD. If I could find a way to mount those and still get the music, I'd never need a CD-ROM ever again.