Don't depend on login passwords to protect your data. To anyone who wants it, your data is easily accessible. A hard drive password is good, but a power-on password or passphrase is better. Enter the word carefully when you set it up since you could lock yourself out of your own machine, maybe for good! PC vendors should be able to help if you receive a message that the PC is protected by a password.
Always leave personal computers in a secure location. If you have to leave the laptop in a car, place it in the locked boot, a locked compartment or similar location. Mark the machine in some way and remember, the more obscure but visible to you the better. Even the most vigilant user may suffer a loss, but with a bit of luck, this article might in some way help you minimize the damage, or even result in a happy ending!