You did follow the instructions as laid out in the document you get on
the HP support page for the 930C about when what is on and when cables
are connected?
If all else fails you could try installing the HP software at this
location:
http://h10025.www1.hp.com/ewfrf/wc/softwareList?
os=228&lc=en&cc=us&dlc=en&product=60096&lang=en
and perhaps try the XP driver?
I got my very old HP Scanjet 5P to run by installing the old HP
Deskscan 2.39 software.