Steganos Safe is a powerful encryption tool with which you can protect your files from things like this. The application works by creating a kind of vault on the hard drive, using a part of the drive to create an external storage unit that no one but you can access.
To keep your files safe, Steganos Safe uses 256-bit passwords, encrypting them as safely as possible. The program includes other secondary features, such as Portable Safe for external hard drives and an eraser with which you can delete all traces of any document or folder from your hard drive.
You can use this version for a maximum of 30 days. To access this trial version, you need to register for free, which you can do from the application's interface.