Hi there and welcome to Eight Forums,
Why are you trying to open MS Word through the Windows Explorer? Do you also get this message when opening MS Word through Start? And have you tried opening MS Word by double clicking a MS Word file?
Do you have a regular installation or are you using a Click-To-Run installation? In the former situation I'd recommend a fresh installation of MS Office. In the latter case I'd recommend a repair of the Click-To-Run installation.
Good luck!
Rover