Download mso9.dll file from the collection of DLL libraries and OCX elements. Perhaps this file will help you to correct the error "the mso9.dll library is not found" which appears as a result of incorrect operation of the Windows operating system or work with the program.
How to download free mso9.dll?
Also, this file may be required when developing software. If you use the mso9.dll file, you should review the copyrights to it.