When you get to the point of 'the "Use other..." option doesn't find it. ', you need to click on 'browse' and locate the .exe file in your Programs.

That is what I have done. I have tried to search for 'okular'. What is the name of the .exe file for okular? There isn't a file "okular.exe". I tried searching just for .exe, using the search in the "brouse" window. I am assuming that this search searches the whole file system (from / root?). The search found five .exe files, none okular. Can it also find "hidden" files? The main question is why doesn't Thunderbird recognise Okular as a valid file to be chosen. It knew about OpenOffice immediately I loaded it.

Do you know the directory (ies) when the Programs are loaded; such as FireFox, Thunderbird, Okular, etc?

Found it and it works! It was in /usr/bin/okular! I use the 'find' command in the Terminal window. I used the 'brouse' window to load it in.

OK, my above question still stands. Why didn't Thunderbird find it automatically? And then, why didn't the search in the browse window find it?

Hi Toad-Hall. Apologies! I should have thanked you for responding to my original email.

There's always (?) an answer. Digging for it can be fun, they tell me :).

I had just located /usr/bin/okular info when you posted back :)