How to change the file manager from Nautilus to Marlin
Solution 1:
To install Marlin in 11.10, enter the following commands in Terminal:
sudo add-apt-repository ppa:marlin-devs/marlin-daily
sudo apt-get update
sudo apt-get install marlin
Source: http://www.webupd8.org/2011/05/elementary-file-browser-marlin-is-now.html
Once Marlin has been installed, follow these instructions to set it as your default file manager:
Open Marlin → Edit → Preferences → click Make my default file manager
Source: http://ubuntuportal.com/marlin-fast-file-browser-and-low-resource-2/