For full disk encryption Bitlocker would be my first port of call, as it's built in to Windows so should be the least hassle, theoretically! Search for bitlocker, it should be relatively painless and hold your hand through the process. You'll choose a password, and store a recovery key somewhere else to allow access in the event of the password being forgotten.
:edit: it's worth mentioning that Bitlocker isn't available to Home versions of Windows. In that case, I'd look towards TrueCrypt, although I've never used it I've heard it is a suitable bitlocker alternative.
:edit2: I meant VeraCrypt, TrueCrypt has been out of development for some time so isn't as secure as alternatives.