Where is file manage preference set

[Alan Chandler <alan@chandlerfamily.org.uk>]

I have a gnome desktop, but haven't always (meaning there are probably 
dot directories with configuration hanging around in my home directory).

I just installed Digikam, and presume it must have brought in Dolphin as 
a dependency, because now when I select "Places/Home Folder" from my 
panel, Dophin starts rather than Nautilus.

I have tried how to change it back so that Nautilus starts, but can't 
find out how.

Any ideas?