Nautilus files viewer

[Keith Powell <keith keithg4jvx force9 co uk>]

Sorry if this is a very "newbie" question.

I have been using KDE for quite a long time, and have decided to give Gnome a 
run.

I am impressed with it, apart from one thing. There are very many files which 
Nautilus says that it does not have a viewer installed for. How do I install  
viewers for these files, please? I can't find a way of adding the missing 
viewers for all the files. Right-clicking on the file and using "Open with a 
viewer or application" only seems to add a viewer for that particular file 
and and not for all the files of that type.

Dare I add that with Konqueror I can view any file?

Many thanks for any help

Cheers

Keith