This installation package could not be opened. Verify that the package exists and that you can access it, or contact the application vendor to verify that this is a valid Windows Installer package.
I've been through a lot of the MS Knowledge Base, and from what I can tell, this problem was recognized and admitted as a Window Installer bug, but should have been fixed as part of Windows XP Service Pack 3. In my case, it was not fixed.
Thanks in advance,