All files corrupt with ext. added ".daapomh" all except video (ie, PDF.daapomh)

All my files for pdf, MS Office, and pictures (everything except videos) now have an added file extension of .daapomh. They will not open and I get a corrupted message. Whatever did this also erased all restore points (or at least it says I have none when I open system restore). I am facing a catastrophic loss of anything not backed up--which is quite a lot of files. I am afraid to simply back up the corrupt files and perform a low-level format, then do a clean install because that may mean not being able to recover any of the files. Has anyone heard of this issue? Google searched turn up nothing for .daapomh issues.