Have you ever accidentally installed a Standalone seat of Autodesk software when you wanted a Network install? Or maybe your company is converting their licenses from network to Standalone. What a hassle. Everyone thinks that you have to uninstall the software and reinstall. But this is not true.
To do this you have to edit your registry, always make a backup copy just in case.
This first came to me from Rob Henriksen. Revit works a little different, in Revit go to the Help pull down and select Produce and License Information.