I've previously found this a bit confusing. This time I did a manual installation by creating a folder C:\MinGW, and then downloading all the relevant dlls on the installation page. To do this quickly just middle click on several links, wait a few seconds, and then hit Save on all the dialog boxes. Once they are all downloaded, move them to C:\MinGW and unzip them there.
No need to install MSYS (a kind of build environment for MinGW) for a project such as Open Babel that uses CMake to build. Why do I mention it then? Because the MinGW page talks all about it.
Compiling Open Babel
1. Add C:\MinGW\bin to the PATH
2. Get Cygwin's stuff off the PATH (if it's there). This is most easily accomplished by renaming C:\Cygwin to C:\oldCygwin or so.
3. Configure CMake to create makefiles for MinGW. I had some problems (at runtime) with a shared library version, so I went with the static one:
cmake -G "MinGW Makefiles" ../openbabel-2.3.2 -DWITH_INCHI=FALSE -DBUILD_SHARED=FALSE4. Build it with MinGW's make.
mingw32-makeHmmm...I wonder if it's as fast as the MSVC-compiled version we distribute?