TrueCrypt is your best bet... It's sort of tricky to use, I recommend the tutorial they have on their website, or surf youtube for a dummy lesson. It's great stuff. I have some of my stuff encrypted with AES 256 bit, Two-fish, and Serpent, with Whirlpool 512 hash, which means it's pretty much unbreakable. However, as with all programs, there are a few holes in it. It's pretty bulletproof though. Also, there is an encryption function with some Microsoft Office products. Goto the menu button, and scroll to "Prepare", then you will see an option for encryption. That isn't the most powerful option though.. I think it only has a 128-bit cipher to it.