We often deal with program-specific disc image formats and would simply like to convert them to ISO. This extension recognized practically by all the programs in circulation.For Windows very simple; you can download AnyToISO which does the conversion from IMG, PDI, CDI, B5I, NRG, MDF, BIN to ISO in one step. The program does not require installation and requires only 157 KB of disk space (also from a USB stick).
To convert the format DMG up Windows (missing in AnyToISO) you can use DMG2ISO.
For MacOSX (Leopard and Tiger) depends on the image format you want to convert and works in the cases listed below.
open the Terminal and used from the command line dd if = image.nrg of = image.iso skip = 300 bs = 1024
normally, just change the file extension from .mdf to .iso
Rename the file from .img to .iso
open the Terminal and use it from the command line hdiutil convert immagine.dmg -format UDTO -o immagine.iso