My Visual Studio 2012 solution has C# projects, VB.NET projects, C++/CLI projects and C++ projects. Currently, I have three platforms: x86, x64 and Win32. When I added x64, I noticed it was used by all projects. I'd like to do the same with x86, so that I can remove Win32.
So I went to Configuration Manager, selected a C++ project and in the platform combo box I only had the options: Win32, x64, New and Edit. If I selected New, the only option available is ARM.
So then I thought of just replacing Win32 with x86 in my .vcxproj. Didn't work (it defaulted to x64). Then I looked at the .sln file, but couldn't see how x64 manages to work for every project.
The IDEs differ too much to get a common platform name for 32-bit code. Otherwise reflective of managed code being rather fundamentally different from C++ code. Managed project platform names can only be AnyCPU, x86, x64. C++ project platform names can only be Win32, x64 and ARM. History plays a role, Win32 comes from the early 1990s, back when Windows NT introduced the 32-bit version of the winapi. Distinguished from the 16-bit version. There was no real opportunity to ever change it again without risking breaking existing projects.
The x86 platform name for managed projects isn't exactly standard either, that was a mistake in VS2010 that you appear to have inherited. VS2012 creates new projects with the AnyCPU platform name like old VS versions used to do. Which pretty accurately describes the true platform for managed code, it runs on any thanks to the jitter. The name is otherwise irrelevant, only the Project + Properties, Build tab settings matter to force a specific jitter to be used at runtime. In other words, if you don't force x86 there then your program is still going to run as a 64-bit process, even though the platform name is x86. That was the VS2010 mistake, it caused a lot of misery.
So you're pretty stuck with this. It is not a real problem, the IDE can handle the mix just fine. You already know about the Build + Configuration Manager dialog, it unambiguously shows which platforms are going to be built when you use Build + Build or press F5.