I had previously gotten a win64 DLL build from the cmake output. I've just opened up the visual studio solution and added a win32 configuration. It seems to build everything properly until it tries to link OpenColorIO - and produces this error:
Linking... .\Release\AllocationOp.obj : fatal error LNK1112: module machine type 'X86' conflicts with target machine type 'x64'
But I've checked all the settings for the Win32 config and I don't see anything set to X64.