If you have important document files you want to keep safe on your computer the best way to go is with TrueCrypt. This program allows you to create an encrypted volume where you can store files, programs, or even an entire operating system.
This program is very simple to use. You first create the volume you want with its size, mount the volume (where it will appear as a real disk), and start packing it with files. Whenever you’re done using these files just unmount the volume and everything is tightly encrypted again. You can even encrypt an entire partition, including your Windows partition. The whole mounting and unmounting process takes just a few seconds.
Another cool feature on TrueCrypt are the hidden volumes. This is where you’ll have a secretive volume inside an encrypted volume. Basically what this means is that you mount a volume with one password and it’ll show you one set of files but if you mount the same volume with another password it’ll show the hidden volume you’ve created. So, there’s actually no way of telling whether you have a hidden volume or not.
Since I try to be as paperless as I can, I scan all my personal documents and keep it all safely stored in an encrypted volume.
TrueCrypt works on Windows, MacOS X, and Linux.