After installing Windows 10 from scratch, I noticed some applications would occasionally need .Net Framework 3.5. If I went to Programs and Features then Windows features to install .Net Framework 3.5, it would ask to download from Windows update which would always fail. I found a KB article at that indicated I would have to use the Windows 10 installation DVD (or ISO) as the source for the updates. This was accomplished by editing Group Policy on the local system:

Going to Computer Configuration -> Administrative Templates -> System

then enabling Specify settings for optional component installation and component repair

then, in the Alternate source file path, point to the DVD or ISO sources\sxs folder


You then need to run the gpupdate /force command then add the .Net Framework 3.5 Windows feature.