Lockdown

Using a strong password is the best way to protect your PC from unauthorized access, but if you're really paranoid, you can configure Windows to temporarily lock the PC anytime the password is guessed wrong multiple times.

Here's a guide to configuring the lockout settings, which require some command-line work on the Home editions of Windows—but once you're done, your PC will be configured to temporarily lock the account any time somebody tries to guess your password a couple of times.