The .NET Framework 4.5 is included with Windows 8 and installed on your computer with the operating system. However, the .NET Framework 3.5 is not automatically installed with Windows 8.
To run applications that require the .NET Framework 3.5 on Windows 8, you must enable version 3.5 on your computer. You can do this via the Control Panel. In Control Panel, choose 'Programs and Features', then choose 'Turn Windows features on or off', and then select the Microsoft .NET Framework 3.5.1 check box.