.iso doesn't stand for anything. its just a common label given to a cd image file. nero by default uses nrg, and there are others too, but they are just an image of the file. and iso is the most common one you will find.
Note that not all CD Writing software images are the same. And most are _not_ the same as .iso files. An .iso file tends to be a RAW dump of an ISO9660 format file system. Uusually extracted with the Unix util dd or created with mkisofs. ISO9660 is the standard file system for data CD- ROMs and DVD-ROMs. ISO9660 was created in the days of DOS and it has many limitations. eg, 8.3 character filenames. Paths limited to 256 characters and such. There is an extension to the format known as Joliet. This allows long and mixed case filenames, longer pathnames. Basically think of it as VFAT for CD-ROMs. Before Joliet came around there was an extension to ISO9660 called Rockridge. This also allowed long filenames and such. However it achieved this by storing TRANS.TBL files in the directories that converted mangled 8.3 character file names to long ones. A lot of Windows CD Writing applications use custom formats that include such things as sub-channel information, CD-Text data, etc. CD's can be quite diverse little critters and each CD Writing app treats this data differently. None of this extra data is part of the ISO9660 filesystem. There are windows apps such as UltraISO (http://www.softaward.com/text/free-download-5231.html) that convert cd images between different formats and some Windows CD-Writing software can read many formats (eg, Alcohol 120%). There is a linux tool called bin2iso that converts CDRWin .bin/cue files to .iso images. They may be others utils for other formats. On Linux you're pretty much limited to .iso files as that is all cdrecord, mkisofs et al can use/create. Another side note. You can use .iso files without burning them to CD-R. Just mount them in loop back mode. eg: mount -t iso9660 -o ro,loop /path/to/cdimage.iso /mnt/cdrom Regards -- Oliver Jones <oliver(a)deeper.co.nz> Deeper Design Limited