If a server is not responding to a client computer, what should be checked next after confirming network connectivity?

When a server is not responding to a client computer and network connectivity has been confirmed, the next logical step is to check the Windows Firewall. Firewalls act as security measures to control incoming and outgoing network traffic based on predetermined security rules. If the firewall is configured incorrectly or is blocking certain ports or services, it could prevent the client from successfully communicating with the server.

By examining the Windows Firewall settings, you can ensure that the necessary ports are open and that exceptions for the required applications or services are correctly configured. This step is fundamental in troubleshooting connectivity issues, as even with a solid network connection, a misconfigured firewall could hinder access to the server.

The other options, while important in their respective areas, are not the most immediate next steps in diagnosing server response issues. Microsoft Update relates to software updates rather than connectivity troubleshooting. Data Execution Prevention focuses on enhancing system security to prevent code execution attacks but doesn't directly impact network communication. Active Directory Domains and Trusts pertains to directory services and authentication within a network environment and wouldn’t be the first target when dealing with a server not responding on the client-side. Hence, checking the Windows Firewall is the most relevant action in this situation.