Hi Jimmy,
You are correct, version 2005 did not have a registration code. The software registration, if I remember correctly, was introduced in version 2008 (v2007 was the last one not requiring users to register the product).
Perhaps you've installed a newer version of S&T on the laptop in the past, and now the old installation is interfering with your attempting to reinstall ST2005.
http://www.laptopgpsworld.com/