Windows 8 Pro/Enterprise/Ultimate have BitLocker built in. There are a few things you need to do in order to get BitLocker to allow the whole disk encryption if your computer does not have a TPM (Trusted Platform Module) device, but I have all my PC's whole disk encrypted with BitLocker.
EDIT: If you do not have Pro(+) and still want a free solution (I know you said no third party...), TrueCrypt
offers whole disk encryption and is freeware.
If you encrypt your drive, use a password you won't forget and make the backup CD. If you lose the password and that disk... you're SOL on getting anything from that drive.
Humans are the only creatures that won't live up to the their potential. Give everything your all. When you die, die on E.
So I ask you, what do you intend to do now?