Install nautilus and use it then. It is a matter of choice. If you do not see it in the menu, you'll need to edit its .desktop file. It will be in /usr/share/applications under the name File Manager. Look for the line OnlyShowIn=Gnome; and change it to ShowIn=Gnome;LXDE;. Do this as superuser (root).
Sorry, I clearly didn't express myself properly. I have
installed nautilus and it does
work (sadly, only via a terminal, since I can't find it in any menu, but at least it does work). However, that's not what I was trying to say in my post. I want to replace pcmanfm with nautilus as the system's standard fm. For example, I have a Directory Menu panel-applet in a side-bar; when I left-click it one of the options is "Open" and selecting this option starts pcmanfm. I want to start nautilus
by selection this option. I assume that there's a config file somewhere or other, which defines which fm is to be started as standard and I'd just like to know where this is. Hope my assumption is correct