A small correction to previous post: two new compiler-and-linker types, not one.

First - MinGW toolset without MSys, working with normal Windows command interpreter, which can be invoked simply by calling "cmd" (or whatever we get from %ComSpec%). Obviously, it doesn't work. Well, it works, but only ~5% of all software packages will have a makefile that doesn't have to be generated by configure script (which we can't run, since this variant of MinGW doesn't have bash) and that doesn't call any shell builtins or *nix tools. On the other hand, SCons, CMake and other build systems not based on autotools should work fine without bash and/or should be able to generate makefiles that don't rely on bash or *nix tools.

Second - MinGW toolset with MSys, working with bash, which can't be invoked by calling "sh.exe" (even if you have full absolute path to sh.exe), because you must cast a few black magic spells by calling sh.exe with "--login" to hook up /etc/profile, which sets up PATH and other environment variables; without it you won't be able to run anything that isn't in c:/msys/1.0/bin - including mingw32-gcc.exe, which lives in c:/mingw/bin, unless you'd want to duplicate /etc/profile in Python (which is possible, remind me to try that), and you have to be careful to not give it any \-separated paths (even in scaped form) at command line, because bash won't understand them, and path mangling doesn't kick in until you're *within* bash, and that includes the name of the script you want to run - it must be /-separated and not absolute (because bash will pass it as $0 without mangling).