It doesn't seem to matter which folder I use but if I go there in Dopus it won't open. Yes, that is the "Metro" reader app. I'm running the released version of Win8 Pro x64. Actually, you can still see the source ISO in my screenshot. As mentioned before, I had the same problem in Win7 using different pdf readers (Sumatra and PDFXchange before that). Some pdfs open fine and some don't. The ones that don't will open fine in Explorer or if I use "Open with" from the right click context menu.