when i mount an iso file to a virtual drive it plays fine, however when on a dvd it doesn't play?

At first, you should note, most dvd players only recognize video DVD well which include a VIDEO_TS folder that have right VOB, IFO and BUP files.

So when you mount your ISO file, you need to check the content in the ISO file, if there is a VIDEO_TS folder in your ISO file which include right VOB, IFO, and BUP files, I think it's a video dvd iso file, you can directly use a right software to burn the ISO file to DVD disc that can be played well on dvd player, but you should note once burn complete, your must close the dvd disc track to finalize the dvd disc, don't use incremental burn mode, if you don't know how to burn, you can try RZ Free DVD Burner, it's free and easy to use, it can directly burn video DVD ISO file to any DVD disc that can be played well on DVD player, easy run RZ Free DVD Burner then select "Burn Image" to burn the video dvd iso file to dvd disc.

Or if there just be some separate video files in your ISO file, such as avi files, mp4 files, mpg file, wmv files, etc, you need to use a right software to convert and burn these video files to video DVD that can be played well on dvd player, you can try RZ DVD Creator, it can directly convert any video files to video dvd and burn to any dvd disc(DVD+R, DVD-R, DVD-RW, DVD+RW, DVD-R DL, DVD+R DL, etc), such as convert and burn avi, mp4, mpg, wmv, mov, etc to video dvd, and the burned video dvd can be played well on your dvd player.

You can yahoo or google search and download RZ Free DVD Burner or RZ DVD Creator, both easy to use, hope them could help you.