Forgive the 'egg-sucking', Keef, but you have done 'Tools/Folder Options/View/apply to all folders' and you "told it to remember each folder's view settings" in the same panel? I am a little puzzled by the reference to the desktop as I have never seen anything other than icons on that. The XP default 'remember folder settings' is, I think, 400.
You place "keep the programmes tidy, by category" in quotes - I must either have a different machine or have missed that link. Where is it?