According to Lenovo here http://support.lenovo.com/en_US/detail.page?LegacyDocID=MIGR-68104
XP does not need a driver for the webcam, which is a bit odd.
Try running Windows Update, and see if that will help.
Also you may want to put what "unable to download" means. You can't find the driver, or you did but can't install it for some reason. Full laptop model # will also help.