Before installing .NET Framework 4.0 by running dotNetFx40_Full_x86_x64.exe:
- Press your Win key and type cmd, then right click on the result and select "run as administrator"
- Once in the command prompt type in command "net stop WuAuServ" to disable windows update
- Then press Win+R and type in "%windir%" at the pop-up window, it will take you to your windows installation folder
- Find the folder "SoftwareDistribution" and rename it to "SoftwareDistribution.old"
- Then, go back your previous command prompt and run the command "net start WuAuServ" to restart windows update
- Finally try again to install .NET Framework