HowTo: Install .NET 3.5 component in Windows 8.1
I just installed .NET 3.5 on a Windows Enterprise 8.1 system that was failing to bring the needed files from the network
To do this I opened a command prompt with elevated rights and ran a single command, having the Windows DVD at drive F:
Dism /online /enable-feature /featurename:NetFx3 /All /Source:F:\sources\sxs /LimitAccess
as explained at this article:
1) if you have the Windows DVD in .ISO file, with a double click it mounts it to a virtual drive on Windows 8, so you can do similarly (you look at My Computer or the folder it opens after mounting to see what drive letter it used)
2) to run command prompt with elevated (administrator) rights, I searched for "cmd" (it is cmd.exe) and right click at the result found to then select "Run as administrator".