Sites like DriverGuide or DriverScape often mirror older, working 64-bit drivers for the D300. Key Downloads for D300:
Official support for the imageCLASS D300 series concluded with Windows XP and Windows Vista. canon imageclass d300 driver
In some instances, Canon’s generic may detect the D300 hardware. This is a "universal" driver intended to support multiple Canon models. While basic printing may function, device-specific features (collation, stapling if applicable) may be disabled. Sites like DriverGuide or DriverScape often mirror older,
the appropriate driver file from the sources listed above. device-specific features (collation
Comprehensive Analysis of the Canon imageCLASS D300 Series: Driver Architecture, Installation Protocols, and Legacy System Compatibility
Windows 10/11 may block old drivers. You may need to disable Driver Signature Enforcement in Windows startup settings to install the 2007-era CARPS driver.