Figure 1 showed the installed modules of my VS2005 and really the x64 tools were not selected for installation. The following step was simple. Just select the x64 item and installed it.
|Fig 1. The original VS2005 had no x64 tools installed|
After the installation, I launched my VS2005 and check the configuration Manager. Figure 2 showed the original Win32 platform option before the installation of the x64 tools.
|Fig 2. There was only a Win32 option before the installation of the x64 tools|
I chose <New...> from Active solution platform and the pull down menu showed the x64 option.
After selecting the x64 configuration, the project had been changed to x64 platform.
Now I could build x64 project with my VS2005. But I doubt when I will use it. :-p
 64-bit and Visual Studio 2005
 How to: Configure Visual C++ Projects to Target 64-Bit Platforms