It sounds like you're looking for the Microsoft-Windows-NetFx3-OnDemand-Package.cab file, which is used to manually install .NET Framework 3.5 on Windows 10 or Windows 11 (usually when the built-in "Features" installation fails).

System Requirements

While modern versions of Windows come with .NET 4.8 or newer pre-installed, many critical applications still rely on .NET Framework 3.5 (which includes versions 2.0 and 3.0). The standard solution is to let Windows Update fetch the files for you. However, when you are offline, dealing with a corrupted system image, or managing multiple enterprise PCs, you need a more reliable method.

Why Use the On-Demand Package?

  • No internet required after downloading the .cab.
  • No Windows Update dependency – ideal for air-gapped or restricted networks.
  • Faster deployment in enterprise environments using DISM or configuration managers.

Bottom line

You usually don't need to download the .cab file manually if you have an internet connection. You can enable it directly: