>Whats the difference between nero's image file and CDRwin[
>file?
Though I can't say for certain, I believe Nero adds track and disc information that a typical ISO doesn't typically handle.* Likewise, they become incompatible with utilities and applications that read "straight" ISO. There's been previous posts about experimentation with .nrg files and (to the best of my knowledge) they weren't met with success.
*Why does CDRWin work then, you ask? Notice that when you create a .bin file it'll also save a file named .cue, which is just plain text that details the session placement and the like. Since these are seperate, I'd imagine that CDRWin doesn't resort to saving information within the image file.