Have you tried running Virtual Clone Drive?
oneThat's what I meant by "mounting" them. It works but there are two drawbacks - it requires another step to mount the file first before playing it, and you can only mount one file at a time.
NOt really true. PLay with the VCD settings. You can assign multiple virtual drives, so that you can mount more than one at a time. Also, you can set it to automount whenever you try to play an ISO in JRiver MC.