It seems that your computer "thinks" your documents are no longer yours and stops you from editing them by making them Read only. There is a technical way to "take ownership" bit I feel you are not up to this so two more simple things to try: - First, go to your "Documents" folder (where I assume your documents are sitting) then Right click on the folder and then left click on "Properties". In the displayed window remove the black dot in the "Read-only" option. This will make all files in "Documents" editable. If this doesn't work then try opening a document then "Save as" (not "save") and give the document the same name but add an extra character to the name so the filename is different ("test1" instead of "test"). This should make the document "yours" and editable. This second option is more long winded because you have to do it for every document. You can then delete your read-only copy and work on the editable copy.
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