Russ' Do It Yourself Home Workshop

If you find yourself needing to use the GACUTIL program to install some "assemblies" (DLLs) in the global assembly cache, you can get it from the Windows SDK.  Now, when you get ready to install, if you don’t need all the other stuff, select the following options.

By selecting only the .NET Framework 4.5 Software Development Kit you will get GACUTIL.EXE installed in the C:\Program Files (x86)\Microsoft SDKs\Windows\v8.0A\bin\NETFX 4.0 Tools folder, at a disk cost of < 75 MB.  Much better and much quicker than over 500 MB!