Hi Rolf, that's great I'm glad it is solved.

As best as I can tell it seems to be a bug in Mixcraft where it must be going through
the registry with its own custom code to find a program to launch under the .pdf file
type.

That's not advisable because it can end up launching a program other than the one
that the OS shell has set as the default handler.

The solution is to call the OS ShellExecute() function instead, passing in the path to
the help .pdf file.

- Michael