Sorry to revive an old thread but I have recently experienced this same problem, but the fix suggested doesn't work.

One day almost all my word documents changed to have the file extension .XML. What is further strange, is the icon for the .XML files can be one of two pictures, colour or Final Cut Pro. The file even has in the description "Kind: Color XML or Kind: FCP XML" I cannot begin to understand what has happened.

I have FCP on a Mac laptop, but these word files were made on a windows laptop at work, and saved on an external HD which I have formatted for Mac and Windows. These files of course were saved on the windows partition.

The only contact they have had with my mac machine is my plugging in the external HD and copying some of the files over to take a look outside work hours.

Now these files are utterly bizarre and have names such as:

Monthly CMD Performance.xls.XML

Then you got ones which are NAME.doc.XML

.url.XML

And hundreds more...

What in blazes has happened, and how would I fix it?