.dmg extension ???

[frichard]

What can you do with a .dmg file ... do you burn it, expand it? i don't have a clue of what to do with that kind of extension ...

[eyelikeart]

Use it in OS X. Like an .img that u use in OS 9 & below.

[GadgetLover]

Assuming that you're talking about what to do with an OS X 10.1.dmg image, you burn it (non mounted) as is in Toast, etc. Toast--and most others--have a selection for "image file" (instead of 'audio' cd or 'files', etc.).

Otherwise, if its just a .dmg file in general which you are asking about, yup, just mount it like a Disc Copy or .img file.