Full disk encryption software encrypts an entire drive, not just a few files or folders. By encrypting your computer’s drives, you keep your private information away from prying eyes, even if your computer is stolen.
Which encryption software do you recommend?
You're not just limited to a hard drive either. External devices like flash drives and external hard drives can also be encrypted with disk encryption software.
There aren't many whole-disk encryption programs that you can use for free. The four I've listed below are the best I've found, which is saying something considering half of them have been discontinued.
These are ranked in order of recommendation based on my experience with each product: