Download the free trial version of Camtasia Studio 3 (28MB) but only version 3. If you want for lastest Camtasia Studio 5 upgrade to it with 50% discount (USD 149). The full price is USD 299
Register yourselves at the promotion page and the registration serial key will send to you by email.
Intall Camtasia Studio 3 and register it with your software key to have a full working version (no expire) version of camtasia studio 3.