Duplex not recognised

You need to set the duplexer to installed. For Vista this would be done as follows: go to the Printers folder, Right Click on the 5550, Run as Administrator, Properties, (continue), Device Settings, Installable Options, Duplex unit (set to Installed), Apply, OK.

Once you have done this in Vista the duplexer will work but the back side may print upside down regardless of the settings. This can be corrected with a patch available here.

Regards,
Bob Headrick, MS MVP Printing/Imaging