You set an open password on your own presentation, forgot it, and PowerPoint now shows a prompt instead of your slides. A PPTX file can have two different locks. A password to open encrypts the whole PPTX, so no slide is readable without it. A password to modify only recommends read-only access, and anyone can still open the deck and save a copy under a new name. Password Remover Tool for PowerPoint handles the first kind. If you remember the password, open the FAQ below for the PowerPoint menu path that clears protection.