I have files that have been on my computer for over a year and all of a sudden they wont open and an error message comes up saying they were improperly downloaded or came in an email attach which is not the case

They seem to be word files - they will open if I choose "open with" microsoft word, but if I double click they don't open they are appearing as PDF on my screen.  I even opened one and then tried to "save as" making sure I chose .doc and they still appear as PDF

I just created a new document response.doc in word and when I saved to my desktop it appears as a PDF file and I absolutely did not create a PDF or save as PDF it was a simple word

doc.

The message says "Adobe reader could not open response.doc because it is either not a supported file type or because the file has been damaged (for example attached in an email and not properly decoded)

The reader version is I believe the most current, I always update when prompted.  OS is Windows 8