Possible Duplicate:
How to install software or upgrade from old unsupported release?
When I am in the update manager, it says that I have to upgrade (You will not get any further security fixes or critical updates. Please upgrade to a later version of Ubuntu Linux.) but when I try, there jumps out a window saying "Authentication failed Authenticating the upgrade failed. There may be a problem with the network or with the server." What shall I do?
