I have looked about in my usual places and the Lexmark site has the most up to date driver. When you download it put it in a folder on its own. (A temporary folder) It should be an executable file ending in .exe) Disconnect the printer. Double click the executable and follow the instructions to install the driver.
Go to Printers and faxes in XP (Start> Printers & Faxes) Delete the printer. Shut down XP and plug in the printer. Restart the computer and XP should find New Hardware and automatically load the new driver. If not post back.