Have you just upgraded to Windows 10 and some of your applications/games ask for the package dotnet 3.5?
Do you get the error message above when the installer tries to connect to the internet and download/install .net 3.5 framework?
You will need an original windows 10 dvd or downloaded ISO image from your windows 10 purchase mounted with something like Daemon tools lite.
You will need the offline installer for dotnet 3.5 (here)
You just need to insert your Windows 10 setup disc in your CD/DVD drive and then select the correct drive letter in the freeware and then click on “Start Installation” button. That’s it. It’ll automatically execute the required command and will install .NET Framework 3.5 in Windows 10.
If you don’t have Windows 10 setup disc or if you don’t want to install .NET Framework 3.5 from setup disc, you can use the setup folder of Windows 10 present on your hard drive. For example, if you copied Windows 10 setup files in E:\ drive of your hard disk, you can click on “Browse” button given in the freeware and then go to the Windows 10 setup folder. Select “sxs” folder present under “sources” folder and then click on “Install” button to install .NET Framework 3.5 in your system.
This small piece of software also provides debugging options for advanced users. You can go to “Configuration” tab and enable the option to show installation process. It’ll help you in finding the culprit in case you face any problem while installing .NET Framework 3.5 in Windows 10.
This software will work in both 32-bit (x86) and 64-bit (x64) editions of Windows 8. You’ll need to run the software with Administrator privileges by right-click on the program icon and select “Run as Administrator” option. Its required because the method only works if the user has Administrator privileges.