Before starting a new discussion topic, please check the Installation FAQ and Upgrading FAQ and try a forum search.
Remember to include in your post which version of Moodle (e.g. 2.8.1) you are using!
(You can find your Moodle version via Settings > Site administration > Notifications.)
Also provide as much relevant background information as you can about the versions and configuration of your server OS, PHP and browser.
(including upgrading and migration help)