Install .NET framework 3.5 offline (really offline) without internet access

some old apps need .NET 2.0 and 3.0

You can use DISM: Deployment Image Servicing and Management (DISM) to add .NET Framework 3.5 and provide access to the \sources\SxS folder on the installation media to an installation of Windows that is not connected to the Internet.

prerequisite:

• Installation media
• Administrator user rights.  

1. Open a command prompt with administrator user rights (Run as Administrator).

2. To install .NET Framework 3.5 from installation media located on the D: drive, use the following command:

DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:d:\sources\sxs