Upgrade to Ubuntu 7.10:

If you already have Ubuntu 7.04 (Feisty Fawn) installed on your system, then you can upgrade Ubuntu without a CD or manually downloading anything.

If you have an older version of Ubuntu than 7.04, then you should backup your data and start with a clean install of 7.10.

Upgrade from Ubuntu Feisty Fawn to Gutsy Gibbon:

IMPORTANT: 

1) First be sure that you have installed all Feisty Fawn updates before proceding with the upgrade to Gutsy Gibbon.

2) Be sure you are online. (Wireless will be much slower than if you are plugged in)

Lets Begin...

Go to System -> Administration -> Update Manager.

Click the Check button to check for new updates.

A message will appear informing you of the availability of the new release.

Click on Upgrade and then follow the on-screen instructions.

Enjoy!