Does anybody know how I can get Excel files to open in Excel, and not let KM think it's a text file and open as such in the browser?

I have got word working ok using the line application/msword (as per registry entry) but no matter what I do, excel files open as text:

]http://www.nw.uklinux.net/test.xls

I have tried application/vnd.ms-excel and application/ms-excel and even application/xls all to no avail.

Nick