I have my code as follows :-
Microsoft.Office.Interop.Excel.Application oXL = null;
Microsoft.Office.Interop.Excel.Sheets sheets;
Application excel = new Mic
I would like to add something to the Eric Bonnot's answer : The answer worked out partially as I worked on a IIS server with a non-admin user with the powerpoint PIA.
I noticed that I could not open a pptx file if this one had a media (picture for example) in it.
The "hack" was to add also the rights to the windows user (the one using the PIA) on the systemprofile/AppData directories.
Hope this helps