When you have a program which needs .NET Framework 2.0, but your Windows system is Windows 8; or, you are a .NET developer, you have old projects were built based on .NET Framework 2.x and you can not convert these projects to newer .NET Framework editions on Windows 8. How can you do ?
Yes, install .NET Framework 2.x.
OK, you searched internet and get .NET Framework 2.x packages, you are ready to install it on Windows 8, but wait, you find nothing happened when you try to install !
Actually, you can NOT install old .NET Framework editions directly on Windows 8. The reason is that all previous .NET Frameworks have been installed with Windows 8, what you have to do is: Enable them.
In Windows 8, run Search, input “turn on feature”, you can see the item "Turn Windows features on or off", click it.
Now you can see all default Windows features, what you should do is that expand the item named ".NET Framework 3.5 (includes .NET 2.0 and 3.0) ", and check on all sub items. then click OK.
Windows 8 now install old .NET frameworks now. Your old projects and programs should work after the feature is on.