Just some information I read about the activation.
Registering Diskeeper

After the Diskeeper installation is complete, you may be given the option to register your Diskeeper purchase online. Be sure to register your Diskeeper purchase to receive the free 90 days of technical support included with Diskeeper.
Diskeeper Activation

You must activate Diskeeper after the installation. This process is simple and fast, and it helps ensure you are running a legitimate copy of Diskeeper. Diskeeper activation requires an active Internet connection, but the activation process is quick and easy to complete.
Diskeeper is primarily designed as a "Set It and Forget It"® disk defragmenter. In order to accomplish this goal, it creates a Windows service, which facilitates communication between the operating system and the individual components that make up Diskeeper. The service allows Diskeeper to run in the background while other applications are running. As long as your operating system is up and running, Diskeeper can defragment your disks, whether you are logged on or not.
After installation, the Diskeeper service starts automatically each time your computer is restarted. The Diskeeper service runs all the time, whether or not defragmentation is occurring. This service consumes negligible system resources, and in most cases will never need to be disabled.