You can also try launching an old application that required .NET 3.5 (like SQL Server 2014 Management Studio or an older game) – it should run without the previous pop-up error. Even with the correct CAB file, you may encounter issues. Here are the most frequent problems and solutions. Error 1: “DISM failed. Error: 0x800f081f – The source files could not be found.” Cause: Windows cannot locate or verify the CAB file signature.
dism /image:C:\ /add-package /packagepath:"%DEPLOYROOT%\Drivers\netfx3.cab" This injects .NET 3.5 into the offline image before first boot. Q1: Is .NET Framework 3.5 safe to install on Windows 11? Yes, it is fully supported and runs in a side-by-side configuration with .NET 4.8. It does not degrade security or performance. Q2: Can I uninstall .NET 3.5 after using this CAB? Yes. Go to Control Panel → Turn Windows features on or off → Uncheck the box. Or use DISM: dism /online /remove-package /packagename:NetFX3~~~~ Q3: The CAB file I downloaded is called “Windows10.0-KB...cab” – is that the same? No. That is a Windows update, not the base .NET 3.5 on-demand package. The base CAB does not contain “KB” in the name. Search again carefully. Q4: Do I need to download separate CABs for x86 and x64? Yes. Installing an x64 CAB on an x86 system will fail with “The package is not applicable to this image.” Q5: My internet is slow. Can I download the CAB on another computer and transfer via USB? Absolutely. That is one of the main reasons to use the offline CAB method. Final Thoughts and Best Practices The microsoft-windows-netfx3-ondemand-package.cab file is a small but mighty tool in the Windows administrator’s arsenal. By downloading it from the official Microsoft Update Catalog, you gain the ability to deploy .NET Framework 3.5 reliably, offline, and without the headaches of the Windows Features GUI. Download Microsoft-windows-netfx3-ondemand-package.cab
@echo off dism /online /add-package /packagepath:\\server\share\netfx3.cab /quiet /loglevel:1 Link this script to a GPO under Computer Configuration → Windows Settings → Scripts → Startup. During Windows deployment (via MDT or OSD in SCCM), add a “Run Command Line” step after the “Apply Operating System” step: You can also try launching an old application that required
Introduction: What is this Mysterious CAB File? If you are a Windows user, IT professional, or system administrator, you have likely encountered a frustrating error message while trying to run older software or games: “This application requires .NET Framework 3.5.” Your first instinct might be to click “Install this feature,” only to watch Windows fail repeatedly, searching endlessly for files that seem to be missing from your local drive or Windows Update servers. Error 1: “DISM failed