The Tennessee Technology Center suggests use of LAlarm

The Tennessee Technology Center suggests use of LAlarm to secure laptops and netbooks. Here is what The Tennessee Technology Center says "If you have an old USB drive, download LAlarm for free and install the software to your laptop or netbook. Use the drive to secure your laptop to the leg of a chair or table. Lock your laptop with the Win+L keys and if the drive is removed an alarm sounds."

Source: http://ttcshelbyville.wordpress.com/2009/11/28/free-laptop-alarm/