I went to open up a ria file I haven't used in 2 months and whaddaya know it says I need to aquire a license.
Your encryption process or whatever you prefer to call it is very flaky.
Until you come up with a better way of protecting your content without inconveniencing legitimate users I won't be spending my money here.
I have plenty of software that has some form authorization but this is the most fallible I've seen.
I urge you to investigate other guitar instruction sites to see what they do.