1 you can tell Windows backup not to include certain folders so say "You can remove E:\ from being copied"
2 i'd assume your scan is being blocked by the usb port turning off if that scan includes any exturnal drives
3 the HP file is putting a 1 in your Windows registry to say this printer is okey... some 3rd party scans assume anything not placed there by Microsoft must be a virus but thats not correct
if you want to keep the printer then tell your virus scanner that file is okey or use a different virus scan software... both are valid options