When you have Word open, use the File>Search command.
With that you can search for a word, or words, contained in a set of documents located over multiple places.

You can select multiple places. Since all your documents are probably in selectable locations (like on a particular drive, or location, i.e. "My Documents") it will be relatively to decide which and where.

You can even select multiple types of files, but since all you mentioned were Word .doc files, that is even easier.

Try it out. Should do pretty much of what you want.