FIXED IT!!!
If you've ever used TuneUp Utilities program, you'll find out there's a disable program function... this is what i used when i was using windows 8.1 to disable my office and adobe reader program. when i upgraded to windows 10, tuneup wasn't compatible, so it was uninstalled, but the effects of the disable function, was still there. so i reinstalled tuneup in a compatible mode and re enabled office and adobe reader 15 and that fixed the problem. Hurray!!!
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Do you have TuneUp Utilities installed by any chance?
I had this very same problem, and it started right after I disabled Office 2013 from the "Disable startup programs" and "Disable programs" tabs. I went there, enabled it back and then went to "Clean registry" (all of this in TuneUp). And now Word is working!
http://answers.microsoft.com/en-us/office/forum/of fice_2013_release-word/windows-cannot-find-winword exe/ef6de2d2-3dee-4b95-8a56-8179682229e0?page=4&au th=1