A:Answer Try https://www.usa.canon.com/internet/portal/us/home/support/details/scanners/support-scanners-canoscan-series/canoscan-d646u.
There are no 64 bit drivers. Cannon says "There is no software for the OS Version you selected." when I chose Windows 10 (64 or 32 bit).
This scanner, D646U, may no longer be supported by manufacturer. Contact Support 1-800-OK-CANON (1-800-652-2666) for an answer.