Have you installed the drivers and software for the scanner? The original software might not be XP compatible in which case you shouldn't install that but download the latest from teh HP website.
http://h20015.www2.hp.com/en/softwa...osoft Windows XP&sw_lang=en&pagetype=software
http://h20015.www2.hp.com/en/softwa...osoft Windows XP&sw_lang=en&pagetype=software