I have and old Canon Scanner (CanonScan LIDE 500F) that I wanted to get working to scan some documents quickly, getting it to work in Windows 10 was not as difficult as I thought.
- Get the Twain Drivers here: https://www.usa.canon.com/internet/portal/us/home/support/details/scanners/support-scanners-canoscan-series/canoscan-lide-500f?tab=drivers_downloads and select Windows 7 (x86 or x64) version
- Download the CanoScan Toolbox v4.9 from the software tab.
- Unpack the Twain Drivers with 7Zip to your desktop (even though it's an exe it will still unzip using 7Zip)
- Plug the Scanner into windows and use the Device Manager to update the drivers on the device by browsing to the folder you unpacked the drivers in the previous location (this is what I did you might be able to just install the drivers with the setup)
- Install the Toolbox software and restart
- Add the following path to the PATH variable in Windows C:\Windows\twain_32\CNQL500
- This is to avoid the "Unable to open TWAIN source" when you try and scan from the toolbox.
You should be able to scan from the toolbox software.