I am unable to print both sides of a document because the PC does not recognise the duplexer fitted to the printer. This has previously worked but I have had a replacment motherboard, hard drive and ram fitted and it no longer works. In the printer properties dialogue box there is no option to print both sides. The printer's control panel shows the presence of the duplexer. In all respects the printer is working well. Any help would be apppreciated.