Install PC Lighthouse, if you haven't already. You can download PC Lighthouse from here.

Start up PC Lighthouse. This can be done either from:

The link on your Desktop (if you had one added during the installation process) OR
From your Start menu (Start » Programs » PC Lighthouse » PC Lighthouse)

From the menu at the top of the screen, select License » Serial Number ... (as shown below)

The window below will open. Enter your Name and Serial Number exactly as it appears in screenshot below. If your Serial Number was not accepted double check for typos.

Another screen will open up asking you to validate your registration. You will need to connect to the Internet to validate your registration, so make sure your Firewall will allow PC Lighthouse access to the Internet.

Press 'OK' to close this window. If your are still having troubles unlocking PC Lighthouse contact us.