Hmm mdf is like iso and or bin, your right. I recognise the format from Alcohol 120%
As for it saying its full, it could be a corrupted file you are trying to download I'm afraid.
It might be worth noting that a recordable DVD can only hold about 4.5GB of storage and the MDF file might have a limit of what it can store (1 DVD size) though .15 might be .5 in real terms
Sorry if it is hehe.
The only option in that case is that it is corrupted in some way
I know its pretty horrid, but is there another you can download of it?
Though you say other people have got it from the same source?
Has your internet connection by any chance got a download limit of what you can download at one time? I know some are weird like that. Like a sort of capped version which would be cheaper.