In order to get Registry Booster active, you need to insert the registration key. You can do this by choosing the option "Register" on the left side of the program. Select the serial number/ registration key. Press Ctrl+C (to COPY), click in the registration field and then press Ctrl+V (to PASTE).
If you lost the serial number, you can request it from the following page :
http://www.liutilities.com/support/regkey/
Please note that the serial number for version 1.x does not work with 2.x
Fore more details on Registry Booster serial numbers, please go to :
http://www.liutilities.com/support/faq/articles/115/