Thanks for the quick reply, but this doesn't really work out for me.
URL rewriting doesn't work with my webhoster. My files are plain text (xml) files. Whenever I click the link to them, my browser opens the file and the addressbar looks like "
http://domain.org/yourwiki//lib/exe/fetch.php?id=pageID&cache=cache&media=namespace:whateverfileyouwant.ext" So I guess there is no way to preserve the filename, because I think the browser uses the first filename in the address bar for saving the file. Am I correct? In this case this would be fetch.php. So without URL rewriting this will always be some sort of .php filename.
The only way could be to tell the browser to popup the little download window whenever the linked file has the Extension ".ext". This is the case for .zip files, for example. Then it could be possible to insert the correct filename into the poupup window. But how can I do that? Does anyone know?