Hide your files and folders so no-one can access them unless they have the password. They will not even know that the files exist.
In this video I show how to create a Virtual Hard Drive and encrypt it using BitLocker and a password.
This works in Windows 7 or newer.
TrueCrypt used to be my favorite method but it reached end-of-life during this year and the official TrueCrypt page now suggests BitLocker as the best next thing.