Once a trial key is expired it can't be reactivated. Basic accounts are limited to 3 keys as this allows creating a key for web, Windows, and phone apps. It is recommended that basic keys are created for doing development and not trial keys. Trial keys
should only be used if running a trial of an app, or handing off source code to another company and you want to ensure they don't take your key and use it for a long time.
http://rbrundritt.wordpress.com