The downloaded codec and filter components are in "appdata". For example, on my XP computer they are in C:\Documents and Settings\[user]\Application Data\J River\Media Center 16\Plugins
You could copy them from some other PC that can access Internet and has MC16 installed.
I did exactly what you proposed. (In that plugins folder of my internet machine there were four folders called dvd_video_decoder, ffdshow, lav, madvr). My computers also are Win XP.
But nevertheless there is still that difference to the internet machine after copying:
If Red October Standard is set at the non-internet machine there is an error message when trying to playback a dvd.
And the following error message occurs when trying to playback a mp4- or avi- or flv-file:
"Error details: DirectShow: Failed to download and install the 'LAV Splitter' filter. Check your network connection and permissions."
So copying those folders and files to C:\Documents and Settings\[user]\Application Data\J River\Media Center 16\Plugins did not work at all!
Is there really no other way??? ?