The Kingdom Download DLL file doesn't appear to be connected with a certain application, therefore I didn't find anything about it in terms of a website, troubleshooting, downloads, installer packages, etc.
If you know what app is that, simply reinstall it because the DLL file is listed in the Startup section, but points to an invalid location. Reinstalling should fix it.
To disable the error, remove the startup software. Go to Start > Run > msconfig and switch to Startup section. From there, locate the Kingdom related software and uncheck it.