This problem is similar to http://davenotes.com/davenotes/node/54 but found with MuseScore software.
PROBLEM:
The following message is displayed when starting MuseScore.
SOLUTION:
Using Edit+Find in REGEDIT, I found a second entry for ctasio.dll. The key pointed to a file C:\Windows\SysWOW64\CTASIO.DLL
Renaming the file to CTASIO.DLL_save removed the warning when starting MuseScore.