I hear what you are saying "I will not uninstall any of my programs, I have no redundant software" but my experience is third party conflicts are nearly always the problem. Despite the Google search it is not really very common.



2010 plays video and sound using "Direct show" (no previous version did) the problem is that Microsoft allows third party programs to modify Direct Show and eg install plug ins and filters. If that sounds like a recipe for disaster... It is (IMHO!)

Have you tried preventing all non Microsoft software running at start up and disabling all AddIns (temporarily). This might at least point to the problem.

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I am sure the problem is with a third party conflict, however as I stated, I can't just fix it by uninstalling a program, mainly because the presentation needs to be accessible to the general public.