You didn’t specify which OS you are running. This link, http://www.hp.com/cposupport/swindexes/hpscanjet318408_swen.html , will take you to a pag with links to drivers for Win 98, ME, 2K & XP. Go there, click on the appropriate OS link and follow the directions.
Go to http://www.hp.com click the drivers and software box the next page will have a space to type in which hp product you have ex.hp scanjet 3300c and next you will click the link for which os you have and you will be at the download page for the drivers be forwarned the drivers are large files from hp usually around 10meg.