Restart your computer.

To execute a true offline installation on Windows 10 64-bit, users typically utilize the Deployment Image Servicing and Management (DISM) tool. This involves mounting the Windows 10 ISO file and running a specific command prompt instruction (e.g., DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:D:\sources\sxs ). This command forces the system to install .NET 3.5 directly from the local source files (the SXS folder) rather than reaching out to the internet. While this method requires more technical proficiency than a simple "double-click" install, it guarantees a 100% success rate regardless of the system's update health.

This method uses the files already present on your Windows 10 install disc or ISO.

. While a "full redistributable" package exists, it often still prompts for an internet connection during setup on Windows 10. Microsoft Learn Method 1: Using Windows 10 Installation Media (Recommended)

Insert your Windows 10 USB drive or mount the Windows 10 ISO file.