You should be able to remove the demo from the DAE/Codecs folder, put the paid version in, and force the authorization dialogue if it doesn't come up automatically. The 5.0.1 MP3 Export serial numbers work with 5.1.The 5.1 CD has both the demo version and the paid version, named "MP3.dll". 5.0.1 CDs did not include the paid version 1.0, also named MP3.dll. When a user downloaded the paid version from the web store, they replaced the demo MP3.dll with the paid MP3.dll.With 5.1, the demo and paid version are both on the CD, and the demo has been renamed to MP3Demo.dll. The paid version 1.1 is named MP3.dll. 5.1 users need the new version to work with 5.1, and also to have both the new Import MP3 feature as well as Export.