Thanks, Ihor. That change worked.
(when (eq system-type 'windows-nt)
(setq org-file-apps
'((\\.\\(docx\\|doc\\)\\'<file://.//(docx/|doc/)/'> . system)
(\\.\\(xlsx\\|xls\\)\\'<file://.//(xlsx/|xls/)/'> . system)
(\\.\\(pdf\\)\\'<file://.//(pdf/)/'> . system)
(\\.\\(pptx\\|ppt\\)\\'<file://.//(pptx/|ppt/)/'> . system)
(auto-mode . emacs))))
