After I upgraded to Windows 10 I was unable to open any attachments in word, excel or PowerPoint. this included old emails I had where I successfully opened word, excel and PowerPoint docs. I tried emailing Microsoft office help and never received a response, logged in using my Microsoft account and found not fixes. I have a Dell OptiPlex. After 3 days of having a meltdown and using my Gmail web account to download said files into google docs, my IT guy found the solution. Hope this helps as I searched forums and Microsoft to no avail... Here is what you need to do. (This applies to Excel, Word and PowerPoint also) Go To Options under the File Tab Click Trust Center then Trust Center Settings Click Protected View then un-click the check boxes. Open Word, open Settings and locate the Trust Center section. Click “Trust Center Settings” and locate the “Protected View” area and uncheck all options.