Hi,
Canon has not released Windows 7 compatible drivers for CanoScan D646U scanner. You may download the XP driver and try to install it in Windows XP compatibility mode in Windows 7.
Here’s the download link:
Refer this article for help:
**http://windows.microsoft.com/en-IN/windows7/Make-older-programs-run-in-this-version-of-Windows**
If that doesn’t help, then please get in touch with **Canon Support** for further assistance.
Regards,
Afzal TaherMicrosoft Support Engineer