Equipping your PC with a firewall and antivirus tool may keep out most hackers, but doesn’t guarantee your security. If someone gets physical access to your system (it’s stolen, say, or a computer repair technician is snooping around) then the best internet security suite will be no use at all, and there’s only one way to ensure you’re protected: Encryption.
Personally i use this open source encryption software called TrueCrypt. TrueCrypt is a software system for establishing and maintaining an on-the-fly-encrypted volume (data storage device). On-the-fly encryption means that data is automatically encrypted or decrypted right before it is loaded or saved, without any user intervention.No data stored on an encrypted volume can be read (decrypted) without using the correct password/keyfiles or correct encryption keys. The entire file system is encrypted (such as file names, folder , contents of every file, free space, meta data and so on).I believe that all of us should have encrypted systems as they protect us from not only virtual  threats but also from snoops or people who just like messing around with personal files on your computer . for example your nosy college roommate who just wants to know where you have the hidden assignment for next days class.
just encrypting your system, drive or file will protect it from from normal users but if
you’re really interested in protecting your data from the government or hackers then use a password that is at least 20 characters long with alphanumerics and special characters. Also ensure that you use upper and lower case  characters AND never use personal information like a dogs name or your birthday as a part of your key!
if you followed everything i said above then CONGRATULATIONS!! you have a very secure device.