I hope this wil help
To change which program starts when you open a file
In My Computer or Windows Explorer, on the View menu, click Folder Options.
Click the File Types tab.
In the list of file types, click the one you want to change.
In Actions, click Open.
In Application used to perform action, enter the program you want to use to open files that have this extension(use the browse function to find Word in Programmes folder) , and then click OK.