If I have a DVD image on my hard disk, can I play that image, or must it be burned to DVD and then that played?

You can use a program which will create a “virtual” dvd drive and can play it back from your hard drive. PowerISO is popular for the PC, the free version will accommodate your needs. Install, restart, set number of virtual drives to 1 by clicking on the “mount” option. Then click open and find your dvd image.

Daemon Tools is free and has disk emulation that will run your DVD image.

VLC should be able to do that. You should just be able to go Media – Open Disc and browse for the disk image you have.

justn is correct. VLC will do it. I do it all the time.

You will need some sort of media player, like VLC. You should be able to just click on the image and it should play in the player. But I highly recommend burning the movie to a disc, in the event your computer crashes.