The driver is here
, you will have to select your OS.
If you have shared the printer, it may not show on the network, but it is available. Have you tried printing using another computer on the network? I think W7 installed the driver for my networked Canon printer, and then printed the document. I had shared my printer in XP, and had to have that computer and the printer on for the W7 machine to find it through the router.