This can happen is the default Program to open .doc files is not set to Microsoft Word. You can check and amend this by:
Open the Windows Start Menu by clicking on the Windows icon in the bottom left of the screen.
Type Default Apps and then select this from the search results which show.
Scroll down and click Choose default apps by file type.
Scroll down until you find the .doc file type.
If this is not associated with Word then click on the default program or the Choose a default option.
Choose Word from this list and this will then be set.