I use Truecrypt for encrypting sensitive data like test reports on my laptop. Truecrypt creates a virtual drive and all files I store there are automatically encrypted. It's simple. That explains its 2 million+ downloads. This Quick Start Tutorial tells you how to get up and running on Truecrypt in 17 steps. It takes about 15 minutes. Here're two additional steps that I'd recommend if you encrypt all your files. These mount the Truecrypt volume automatically every time you log on to Windows. (Yes, it prompts you for a password.) Step 18. Select Volumes -> Save Currently Mounted Volumes as Favorite
Step 19. In Settings -> Preferences... enable "Start Truecrypt" and "Mount Favorite Volumes"
Next time you login to Windows, Truecrypt will mount your encrypted volume automatically.