HOWTO: Replace Nautilus with PCMan (4 Steps, No Fuss).
1.
Install pcmanfm from the package manager.
Quote:
Applications > System Tools > PCMan File Manager
2.
If you find that you like PCMan and want to have "Places" use it instead of nautilus do the following:
Start the PCMan File Manager and go to:
Quote:
/usr/share/applications
In PCMan "Open Current Folder as root"
Quote:
Tools > Open Current Folder as root.
3.
Make a backup copy of the files below (copy and paste and add "_bak" on the end of the file name.
Quote:
/usr/share/applications/nautilus-computer.desktop
/usr/share/applications/nautilus-folder-handler.desktop
4.
Change the line in each with starts with Exec=
e.g
Quote:
For nautilus-computer.desktop: Exec=pcmanfm /
For nautilus-folder-handler.desktop: Exec=pcmanfm %U
Done 
o completly replace nautilus follow this steps, they all are reversable and not harmful at all, as long as you make the backups.
First we need to backup some files
Quote:
sudo cp /usr/share/applications/nautilus.desktop /usr/share/applications/nautilus.desktop.backup
sudo cp /usr/share/applications/nautilus-folder-handler.desktop /usr/share/applications/nautilus-folder-handler.desktop.backup
Then open these files
Quote:
sudo gedit /usr/share/applications/nautilus-folder-handler.desktop
sudo gedit /usr/share/applications/nautilus.desktop
and replace every nautilus word with pcmanfm (delete the arguments after the word pcmanfm since some are not supported)
And save
And these changes are for gnome session manager(so ubuntu stops trying to load nautilus)
Backup this file
Quote:
sudo cp /usr/share/gnome/default.session /usr/share/gnome/default.session.backup
Then we need to delete a few lines an change some numbers
Quote:
sudo gedit /usr/share/gnome/default.session
Then open it and delete the lines that have at the beggining the same number as the nautilus line
something like this:
Quote:
2,id=default2
2,Priority=40
2,RestartCommand=nautilus --no-default-window --sm-client-id default2
Then rename the other lines so the numbers dont jump from 1 to 3.
And from the line
Quote:
num_clients=X
Change the number to the new number of process you just changed.
And save
If you don't understand i added my file to this post as an attachment so you can compare.
And the most important step to kill nautilis you need to do this :
Quote:
sudo cp /usr/bin/nautilus /usr/bin/nautilus.backup
sudo rm /usr/bin/nautilus
sudo ln -s /usr/bin/pcmanfm /usr/bin/nautilus
Finally, you need to open a PCMan window and go to edit, preferences, desktop, to configure the desktop.
And dont forget to restart the session doing ctrl+alt+backspace
Doing this ubuntu wont ever load nautilus, saving the precious ram and reducing boot time.
I wish you could just uninstall it, but the package is tied to many other important packages.