How do I setup duplex printing in Windows XP?
Instructions for configuring duplex printing for printers that are already installed on your computer are located here.
Once you have installed duplex printing, you need to specify printing on both pages in whatever program you use. In Microsoft programs (IE, Word, Excel, etc.) click on the Properties button in the print dialogue box. Under the Layout tab there will be a box that reads Print on both sides. Click on the radio button next to the Flip on long edge selection in this box. Apply this change and you will be able to print on both sides of the page on that particular printer.
This procedure can be followed for any printer on the network that has a duplexing unit installed. A list of duplexing capable printers can be found here.