All my pdf and word documents ruined or corrupted at the same time!!

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What could be the posssible reason that destroyed my prescious pdf and word documents in a split second. I tried to open every acrobat file in my lap but everything was destroyed. When I try to open it there pops a message " There was an error opening this document. The file is damaged and could not be repaired." Also " Format error. Not pdf or corrupted." I opened it in notepad and noticed that there is a repeated word in it- dulla 204... I don't know how to write it. I have the latest antivirus but couldn't get it. Does anyone have a clue? Thx.