from: http://quefyx.com/2009/05/26/upgrading-ubuntu-9-04-jaunty-to-9-10-karmic-on-eee-pc-seashell/
Make sure the APT repository is updated:
sudo apt-get update
Make sure Update Manager is installed and up to date (which it should be):
sudo apt-get install update-manager
Now run the Update Manager from Terminal:
sudo update-manager -d
You will see an option “New distribution release ‘9.10′ is available”. Click the Upgrade button to upgrade and follow the prompts to upgrade your distribution.