How to convert an .nrg file to iso?

No, nrg is not "just" a change of extension!

But the change is minor, it's true: Nero adds a header at the beginning of the iso image. So under Linux:

dd if=image.nrg of=image.iso bs=2048 skip=150

Translation for Windows enthusiasts as well as for penguin lovers:

The data block is 2048 bytes in size: bs=2048
Skipping the first 150 data blocks: skip=150
Raw copy of the image file image.nrg into image.iso: dd if=image.nrg of=image.iso bs=2048 skip=150

There you go, we've created a clean iso image free of its nrg header, the purpose of which I do not know, but if Nero included it, there must be a valid reason.

I suppose it must be just as easy to do on Windows without additional software, but I'm not very familiar with the commands.

There you go, the thread is a bit old, but since it is well referenced and still relevant, it’s worth clarifying the information.