just uninstall and reinstall microsoft word, it’s the simplest way

or you can manually configure program defaults via the control panel. or just right click on any document type you want to open in word, chose “open with” and than highlight microsoft word, and check the box that says “always open this file type with this program”

Open “My Computer”, click Tools -> Folder Options…Select FileTypes. Look for DOC extension and click change button and look for Microsoft Word.

right click on what you want to open and go to properties, than go to open with and click change, than click on microsoft work, than click on the box at the bottom

Try this:

In Windows XP:

1.In Windows Explorer, find a .doc file. (.docx file for Word 2007)
2.Right-click on it and select Open With.
3.If MS Word shows up, select it.
4.If it does not, click the Browse button. Navigate to the directory C:\Program Files\Microsoft Office\Office10 (Office10 for Word 2002 (XP), Office11 for Word 2003, Office 12 for Word 2007). Find and select the file winword.exe.
5.In either case, check the checkbox Always use the selected program to open this kind of file.
6.Click OK.

In Windows Vista:

1.In Windows Explorer, find a .doc file. (.docx file for Word 2007)
2.Right-click on it and select Open With. If a menu pops up, select Choose Default Program.
3.Go to Step 3, above.

Hope that helps.