I suspect that your DB parameters are set to default and database is not running in an archive mode as archive_mode = off , I believe PostgreSQL won't write archives when archive_mode is off and WAL archival cannot be enabled when wal_level is "minimal".
I assume the existing 200GB worth of archived wal files are old where you can verify by checking the timestamp of the Wal files and remove.
If you want to disable/enable archive_command you can simply comment/uncomment parameter and reload the server to affect but for
enabling archive_mode = on server required a restart.
Could you please advice how I can cleanup all of these 200GB worth of files.
I've searched through numerous postgresql books/blogs/articles which all have very good advise on how to setup wal archiving but unfortunately not on how to disable it.