Was this installed by disk with software or did you get the driver and software from website.
You need to uninstall the software and make sure the driver was uninstalled. First go to my com,properties, hardware, devise mgr,
and look in this list for the driver,lexmark printer. Now use add/remove programs and uninstall the lexmark stuff, now restart pc, and check devise mgr and make sure its gone,if not just rt click on it and pick uninstall,restart pc. Now run the registry cleaner.
Download this free registry cleaner, its pretty good for free.
Run the cleaner, and then download the driver,make sure vista driver, from page that I post below. Now reinstall the software
and follow the directions when it tell you to hook up the printer.
Registry cleaner;;
http://www.ccleaner.com/downloadDriver page.
http://downloads.lexmark.com/perl/downloads/downloads.cgi#You will have to research the driver as the page does not hold the driver.