This is not an Office choice, but a Windows feature. To hide the file extensions on all files, go to Control Panel/Folder Options and select the View tab. Scroll down just a bit and "check" the Hide file extensions.

Thanks Ulodesk.
So will a trapdoor open 'neath my feet when I do that?

And before you know it, you'll be in Bill Gate's living room -- which, but the way, is reported to have windows.

E-gads, man!
I've been by that fortress in my boat and that is the last place I would want to end up. Now I know why the dire warning from Mr. Kenyon; he must have encountered Gates gallows.

Really though, all other PCs have been extension-less forever without issue so I went ahead and followed your path.
Thank you.