Swamp thing is right on this, Nearly every ISO image I've made is way over 700 mp for full discs. You have to use the "Burn Image" option under the File menu and select the ISO for burning. Do NOT add the .ISO image to a new compliation or anything like that. When using the Burn Image method, you will be asked for an .NRG image file. Ignore that and make it look for All Files and select your .ISO file. Nero should "Translate" the ISO into the proper CDDA Filesystem format, fitting the data onto the disc. You cant just burn the .ISO file to disc because the .ISO file is an IMAGE. Images will include extra information such as disk geometry, etc, usually. If you burn the image file itself onto CD, you'd be burning that extra 50 mb. If you have nero "translate" the image into a real CDDA filesystem format, it will fit - In theory.