To install .NET Framework 3 in offline mode on Windows 8, you need your installation iso / flashdisk drive with the windows installation or windows installation cd, then type this on Command Prompt with admin
1 | Dism /online /enable-feature /featurename:NetFx3 /All /Source:F:\sources\sxs /LimitAccess |
type the drive where your windows installation is located, for my case it’s in drive F.
Give it a try 😀