I 2nd the VeraCrypt or TrueCrypt
There are so many free options out there to encrypt drives.
Pretty much any legit encryption software out there will be "military grade"
2 downsides to using them
Accessing your data will be slightly slower on an SSD, and a bit slower on a HHD.
If you ever forget your key you are screwed.
edit: Cracking passwords on these can be brute forced though, so with a normal 8 digit letters and numbers only password, a good computer could crack it in days. You will want numbers, letters symbols, upper and lower case, and do 8-14 digits long.
This site shows you how secure your passwords are.
http://random-ize.com/how-long-to-hack-pass/