Re: I have been able to open PDF docs using C# API Process.Start("Full_path_To_the_PDF_File") in windows 7 or windows 8 with all previous versions of Acrobat32 reader.

I haven't use the C# API but I imagine it is the same as C ShellExecute. Which in turn is the same thing (in essence) as double clicking in Windows Explorer.

So... does Adobe Reader run normally on this machine?

And does it start and open if you double click on a PDF file?