Canon Scanner Drivers Not Installing to XP

XP Sp2, fully updated, was working with Canon Pixma 830 mulifunction device. At some point, scanner stopped working (printer still communicating and working). Device Manager has yellowed exclamation point before device, clicking on device names says registery is either corrupted or missing (code 19). Have spent 6 hours on phone with Canon and Windows reinstalling drivers in evrery conceivable manner (from Safe mode up), always same results; printer but no scanner. Any ideas?