The Purchase menu contains the following items, when Audion has not yet been registered/purchased:

Audion Home Page
Takes you straight to the Audion home page.

Purchase Audion On-Line...
Takes you to the easy, simple Audion purchase web page.

Sign up for Audion eList...
Lets you sign up for the Audion eList and receive updates when new versions of Audion are released.

Enter Serial Number...
Prompts you to enter your Audion serial number, given to you when you purchased Audion, which unlocks the full version and removes any restrictions.