Prey is software that enables you to track down your Ubuntu, Windows or even mac laptop or netbook. It's open source and the use of it is free when used for a couple of machines only.
Go to http://preyproject.com/ and download and install the software.
After downloading make an account and you're done. You can use the software on android machines too. There are no blackberry and Iphone or Ipad versions yet.
The free account lets you use prey on 3 machines. If you need more functions or more machines you need to pay. It's not really cheap. But to find your stolen laptop is a great idea.
If you're dualbooting on a machine install it in both OS's. To do this, start by installing Prey on your first OS. Once you’re set, install it on the second OS by selecting the “Existing user” option. The installer will create a second device under your account. Delete it and copy the device key from the other device’s management page (the one created by the first install). Then you need to open up the config file on the second OS and replace the device_key for the one you just copied. That’s it. Now, when requesting reports or triggering actions, Prey will do its job regardless of the OS being run at that moment.
Prey can only be uninstalled if the thief knows the administrator or super user password. To prevent him from doing so they encourage you to add a BIOS password and disable booting from removable devices on your PC, so that the thief will be forced to boot into the previous installation and thus, not be able to format your hard disk easily.
If you have a Mac, there’s a firmware password utility on your Mac OS installation DVD. You can find it in in Applications/Utilities on the disc.