Attempting to run these applications without .NET 3.5 typically results in a dialog box: "This application requires .NET Framework 3.5. Install now?" Without it, the application will crash or function incorrectly.

While no one should start a new greenfield project on .NET 3.5 today, knowing how to enable it via Windows Features, repair it with DISM, and secure it with modern policies will save countless hours of frustration. The framework may be from 2007, but for many critical systems, it remains as essential as the day it launched.

For most users on Windows 10 or 11, this is the simplest path: