If you are unable to install .NET Framework 3.5 (.NET 3.5) on Windows 8.1 or Windows 10 and end up with errors like 0x800F0906 and 0x800F081F you will find that errors relate to corrupt or limited access to the source files. In ALL of the times I have tried to get around this, the source has NOT been the issue.
Often you can just install .NET 3.5 by bringing up a CMD window (don’t forget to right click and RUN AS ADMININISTRATOR) and then type either:
DISM /Online /Enable-Feature /FeatureName:NetFx3 /All
Installing .NET Framework 3.5 from the Control Panel
If you want to install .NET Framework 2.0 and 3.5 yourself, you can follow the steps below:
Go to Control Panel –> Programs and Features (Windows Key + X + F)
On the left hand menu, select Turn Windows Features on or off. You can also open this directly using Run –> Optional Features
This will download all the required components from the Internet and automatically install the framework for you.