Using the Activation Server to create the Unlock Key ensures, that the Serial Number can not be used twice (e.g. customers sends the Serial Number key by fax and uses the key on another PC with Online activation).
Log into the Web Administration Interface and select Administration / Setup, Manual Product Activation.
Complete description - Create Unlock Key on the Activation Server / Manual Product Activation
See also
Explanation of all installation codes
Unlock Key - all options