[LacrimansTaurne]

Sometimes programs will run hidden, and ctrl+alt+del won't close them all. After you closed everything you can through ctrl+alt+del, go to System Information (under System Tools) and click on Software Environment, then Running Tasks. This will show you what programs are still running. You'll probably have to uninstall some stuff in order to defrag. I know for a fact that having Realplayer installed on your computer can mess with defrag. Good luck.