Ubuntu automatically installs python 2.5 and uses it as the default python … I have crashed my system 2 times to solve this .. I wanted to make the default python to version 2.4. This is the way before begaining Thanks to (Luiz Rocha (lsdr) ) http://ubuntuforums.org/showthread.php?t=440358 and http://www.gossamer-threads.com/lists/python/python/685071 First, edit the /usr/share/python/debian_defaults, changing the default version arg to python2.4 2nd, $ sudo mv /usr/bin/python /usr/bin/python25 $ sudo ln -s /usr/bin/python2.4 /usr/bin/python reference( http://tareqalam.wordpress.com/2008/11/28/change-the-default-python-version-in-ubuntu/ )