As a mobile worker for a government agency, I am constantly aware of the vulnerability of my notebook. The portability that I value so highly also makes it an easy target for thieves in places such as airports, cafes, and even serviced apartments and shared offices. Not only is the actual device more vulnerable than a desktop PC, the data stored on the hard drive needs to be secured as well.
One of the best ways of securing the data, even if the device is lost or stolen, is to protect it with System Administrator and HDD passwords. The system 'boot' password prevents would-be hackers from bypassing the user login screen by going straight to the BIOS, and the HDD password prevents a persistent hacker from physically removing the hard drive and placing it in another machine, thus circumventing any device-specific security.
From a cold start press F12 to set Boot Options. The Security area allows you to set an Admin, System and HDD password. Note that securing the HDD with a password means that a recovery password provided by Dell will cause all data on the hard drive to be erased. This security feature prevents a thief from stealing your device and contacting the manufacturer claiming to have forgotten the system password. It also means that if you forget your password you risk losing all your data. So back it up in a secure environment like SpiderOak, and store your password in a safe place such as SecureSafe.