If you have recently downloaded and installed Windows 8 RTM, you may begin finding applications that require the usage of .Net Framework v. 3.5.
Unfortunately, unlike its predecessor--Windows 7, Windows 8 ships with .Net v. 4.5.
Well, that poses a bit of a problem because of the new installation infrastructure that was implemented with Windows 8 whereby the installation media/installation source is required when installing any additional Windows features. This new mechanism of installation is called DISM and you can read more about it here: http://technet.microsoft.com/en-us/library/hh824821.aspx
If you encounter and read this article regarding DISM and .Net 3.5, you will see that it primarily addresses the issue in Windows Server 2012 and only provides a cursory overview of how to solve it in Windows 8: http://blogs.technet.com/b/askcore/archive/2012/05/14/windows-8-and-net-framework-3-5.aspx
The key to installing .Net 3.5 on Windows 8 actually lies in the first few steps:
- Open up gpedit.msc
- Edit the Group Policy under Computer Configuration-->Administrative Templates-->System
- Open the policy for Specify settings for optional component installation and repair.
- Specify an alternate source file path for the files (preferably a file path directly to the ISO image/Windows 8 media). You can also optionally check the checkbox for "Never attempt to download payload from Windows Update"
- Click OK to close the Group Policy Editor
- Now open Control Panel-->Programs and Features
- Click on "Turn Windows Features on or off" in the left hand navigation
- Click on the checkbox for ".NET Framework 3.5 (includes .NET 2.0 and 3.0)
- Click the OK button to proceed with the installation
If all goes well, you should be able to successfully install .NET 3.5 on your Windows 8 RTM machine!