The 64 bit compiler is included in the Windows SDK 7.1.
If you try to install Windows SDK 7.1 on top of Visual C++ 2010 SP1 the installation process will fail.
Unfortunately the failure dialog that pops up after the installation failure gives no clue as to where the problem lies. You can open the failure log from the dialog but again the error messages do not provide a direct source of the problem.
Performing an internet search for solutions show up a lot of people having the same problem and a lot of other people not quite knowing the solution. One example of erroneous suggestion I came across was to install from the ISO rather than the web install.
Fortunately, those clever people at Mathworks have published a great set of instructions here to explain how to correctly install the 64 bit compiler :
A quick summary of the procedure is :
Uninstall the Visual C++ 2010 Redistributable packages
Install the SDK 7.1
Apply the compiler patch from Microsoft
Reinstall the Visual C++ 2010 Redistributable packages