syntax highlighting in Netbeans for files,which are not automatically recognized because of naming

I have some makefiles with "unusual" extensions. So Netbeans does not
recognize this files as makefiles and opens in a simple text editor.
To get the syntax highlighting in Netbeans 6.7.1 use the context menu
and select "Open As".
A new dialog appears, where you select the type of file as which this should be
opened.

Now the before "unknown" file has also the syntax highlighting.

Under Tools/Options/Miscellaneous/Files you find the association between
the file extension and the Mime-Type. Here you can change it, if you do not
like it.