A DVD consitsts of files with IFO, VOB and BUP extensions. Each IFO will have a BUP as a copy (it is a BackUP). The VOBs are Video OBjects and contain all the video, audio and subtitle info.
Your ISO is a container of these files. It should be 4Gb+. If so, just open ImgBurn, go to Write mode, load up the ISO, pop in a blank (good quality one, of course) and hit the big green button. I advise you to turn on verify.
Any problems, post the log.
Regards