FAQ: How do I add new licenses to SQL Server 2005 or How do I change the licensing mode
In previous versions of SQL Server there was a licensing app that was integrated into control panel and was exposed via setup. It allowed you to enter the type of license you had for your server(Server+CAL or per CPU) and if you were using a CAL option then it allowed you to increase the number of CALs.
Lots of people have asked how to do this in SQL Server 2005 as the tool no longer appears to be there. Thats correct the tool is no longer there but there is a new licensing scheme, its based on integrity...
In other words in the current version there is no tool, you are not prompted to enter license model and in fact if you query the server for license mode it shoudl return disabled.