Have you gone to the Photoshop Help menu and selected Help > Activate... You need an internet connection to do this. All you have to do is follow the steps.
What is activation? Photoshop used to be unlocked with a serial number only. However software pirates simply passed the numbers around to unlock multiple copies without paying for the license.
As of Photoshop CS3, activation requires a connection to a remote server that validates the machine it was installed on on order to launch Photoshop. You are allowed to activate on two computers. Any change in hardware means you have re-activate.
We are basically volunteers not Adobe employees. If you cannot activate your copy as instructed, call customer service and they can help you by resetting the activations.
Unless you signed up for email notifications, it's best to recheck the forums to see if anyone answered your question.
Gene