You can go to Lexmark support download page. You'll have to enter the operating system you're using. (i.e. Windows XP etc) and download the driver for the 1150 to a place in your computer where you can easily find it, maybe the desktop. Once you've downloaded it got to START, the RUN and BROWSE and point to the file you downloaded. Follow the instructions on your screen.
Here's the link to the driver you're looking for:
http://downloads.lexmark.com/cgi-perl/downloads.cgi?ccs=229:1:0:0:0:0
Bruce
June 2008