: The system believes the device is already registered, preventing a fresh installation. Step-by-Step Solutions 1. Perform a Clean Cleanup with KT Uninstaller
Run the utility and select under the Product family.
: Leftover configurations from old versions interfering with new driver registration.
Perform the cleanup for both versions to ensure all registry entries are wiped. Restart your computer immediately after the cleanup. 2. Manually Remove Drivers and Registry Keys If the uninstaller fails, manual intervention is required:
Standard uninstallation often leaves behind registry keys that trigger Error 28201.
: Press Win + R , type regedit , and navigate to HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Kerio . Delete the Kerio key.