If you ever leave your computer unattended, share it with others, use a laptop or work on a network, you need DiskLock.
DiskLock is as easy to set up as pressing a few buttons, yet it's virtually impossible to defeat.
From the authors: Foolproof protection. DiskLock sets up much faster than other security programs. Instead of having to select each file, you can choose entire folders with a single click. And DiskLock is virtually impossible to bypass - it loads before the system software, so unauthorized users can't start up your system, even from a floppy disk.
Important note: Before using this program, be sure to read all the documentation in order to avoid problems. For more detailed information, be sure to visit the home page. They have a manual that can be downloaded from their site.