If you're having trouble with GTKRadiant 1.4 then this tutorial is for you (http://www.katsbits.com/tutorials/idtech/gtkradiant-1.4-setup-and-editing-idtech3-games.php). Covers the basic set up and use for custom content as well as some of the common errors that happen whilst using the application on Windows Vista machines (it wasn't built to run on Vista).