1. method

if you installed openerp in an Ubuntu or Debian distribution, do this:

apt-get search openerp-server openerp-client

if the application is installed do this:

sudo apt-get remove openerp-server openerp-client

2.

http://dokgikom.blogspot.in/2012/07/how-to-remove-openerp-from-linux-solved.html

3.

Their is no need to uninstall, just update the software. If you want to install a new version of the server and the webserver on Ubuntu server you can follow this instruction:

http://forum.openerp.com/forum/topic24214.html

In this procedure change the parameters/values to your needs.