1 open cmd
2 type in command "net stop WuAuServ" (disable windows update)
3 Go to Run (you can do this by pressing Win + R) and type in "%windir%" (this command let you go to your windows system folder)
4 Find the folder "SoftwareDistribution" and rename it as "SDold"
5 Then, go back your previous command p
6 prompt and run the command "net start WuAuServ"
Now, try to install .NET Framework again