The GCK installer includes prerequisites that have been found to be "usually needed".   For example, it will install on a server system that comes straight from Dell computers.  (Something done regularly at the factory.)  However, some users may find that their version of Windows may not have all the prerequisites that are needed.  Rather than build all the prerequisites into the GCK installer, ballooning it to a very large, slow to download size for all users, we've created a separate (half gigabyte) prerequisite installer for those users who find they cannot install GCK because it is looking to load a Windows feature or connect to the internet to get a prerequisite package.  This installer may be downloaded from here (IED DotNet Framework Prerequisites).