Let's deal with the Word and Excel files first. The operating system isn't involved here - they are both Microsoft Office applications, so provided you have Office installed on both machines you can open and edit the files in either of the two Windows versions.
Ditto for Outlook, it's an MS Office programme too. You can export the contacts list, for instance, from one machine's Outlook to a file, and then import the file to the other machine over the network. Again, nothing will happen unless you have MS Office installed on the Desktop machine.
Outlook Express is no longer in existence.