Windows 7: Need printer driver for Lexmark Optra S 1855

I have a new HP Pavillion laptop running Windows 7 on a home network. I have a Dell Windows XP laptop on the network I am using for a printer driver, and a Lexmark Optra S 1855 laser printer connected to the Dell XP machine parallel printer port. I also have two Windows Vista computers on the network and have no problem printing to the Lexmark from them or the XP machine. The Windows 7 laptop can find the Lexmark on the network but can't find a driver for it. The Lexmark web site says to use the internal Windows printer driver but the printer installation program in Control Panel can't find it (it is looking for a ,inf file that apparently does not exist).

Does anyone have any suggestions? I love my Lexmark and really hope I can get it working from the new Windows 7 machine.