File extension problem under KDE

Hello,

sorry for the stupid question,

but I have a problem and haven't found any solution to it on this forum so far.

The problem is how to recognize different file types under KDE.

I have Mathematica files (with extension .nb and plain text format).

I want them to be opened with Mathematica.

I try to edit them as [Right-click]Properties>Settings>... and choose Filename patterns *.nb *.NB to be declared as Mathematica notebooks and opened with Mathematica. But after this all the plain text files (.txt, .cpp, .h ) are opened with Mathematica. When I declare these (.txt, .cpp, .h ) to be opened with KWrite, Mathematica notebooks are also opened with KWrite.

How is it possible to make KDE aware of the new filetypes ?

Thanks in advance,

Xaleandr

PS: Below are the first few lines of .nb-file if this might help:

Code:

`(************** Content-type: application/mathematica **************`

CreatedBy='Mathematica 5.2'

Mathematica-Compatible Notebook