From the actual download link >"Installing a CTP release will place a computer in an unsupported state. For that reason, we recommend only installing CTP relea

From the actual download link >"Installing a CTP release will place a computer in an unsupported state. For that reason, we recommend only installing CTP releases in a virtual machine, or on a computer that is available for reformatting. >Currently, Visual Studio "14" CTPs have known compatibility issues with previous releases of Visual Studio and should not be installed side-by-side on the same computer." I don't know how serious that statement is, or maybe it's just a big blanket clause. But it seems like they really, really think you shouldn't install them together.