I recieved this message on occasion and it was particularly frustrating because not only does it say in the message "please reinstall itunes" which does absolutely nothing, but the method that itunes has for resolving this problem (http://support.apple.com/kb/TS2372) to the common user, is incomprehensible and not that reliable.
So for those of you out there experiencing this problem, i have posted a copy of a clean registry key for itunes.
You need only download the file and run it, and it will replace the registry key with the one itunes is looking for.
Itunes Registry