It shows the file type as FILE because there in no extension to the file name.
Rename the file to <whatever>.iso or .nrg or .bin and open with a relevant software to see if it works.
Even if you dont rename it ... opening it with relevant software would make it work. If it's actually a zip file, then it would open with WinRAR .. if it's actually a video, it would run in a player, etc
You need to forcefully ask the software to open the file ... try this with different (possible) softwares .. try your luck.
It could be an excutable too .. rename it to .exe to see !
If you still dont know what it is .. you can try using TrID
It's command prompt based utility to compare binary signatures of files to identify what they are.
Try that.
About NFO viewers ... Notepad usually works for me .. Never used anything else.
Sorry cant help you there.
But if you want .. mail me over that nfo file to my.alibi[at]gmail[dot]com .. I'll try whatever I can.
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alibi