I have a Phaser 6121MFP (with duplex unit) connected to a Windows XP PC by USB and shared in the LAN with Windows 7 PCs. The PCs using Windows 7 can't set duplex printing (the combo 2 side printing is grayed). Is it possible to override printer setting on the Windows 7 driver to add (force) duplex unit? I cant find it!
you must enable the option in the driver if using USB, open up the properties, there you will find a tab with bidirectional settings, disable that one and setup manually
then you can enable the duplex unit, that will make the duplex option avaible
you dont have todo it on the port settings, but in the options tab of the driver...
do you see the device options there ?
maybe you can try to use the global driver, the option is 100% avaible there :)