how to recover or restore (dnssd.dll)

Hello, kalminex. Welcome to the Apple Support Communities. 

We understand that you may be seeing a message on your Windows PC that an iTunes program file may be missing. We’re glad to see that you have already been able to start on the Apple Support website and we would be happy to help you continue from here. 

For something like this, it may be best to reinstall iTunes on your PC. You can download the iTunes program and components for the version of Windows that you have installed at this time. 

To be safe, we would also suggest creating a backup of your music library before reinstalling iTunes. The following Apple Support articles can help explain more: 

Back up and restore your iTunes library on your PC - Apple Support

Remove and reinstall iTunes and related software components for Windows 7 and later - Apple Support

We hope that this solution works for you. Please let us know if you have any other questions!