Note: this section is out of date. GStreamer-0.10 has much better support for win32 than previous versions though and should usually compile and work out-of-the-box both using MSYS/MinGW or Microsoft compilers. The GStreamer web site and the mailing list archives are a good place to check the latest win32-related news.
There are different makefiles that can be used to build GStreamer with the usual Microsoft compiling tools.
The Makefile is meant to be used with the GNU make program and the free version of the Microsoft compiler (http://msdn.microsoft.com/visualc/vctoolkit2003/). You also have to modify your system environment variables to use it from the command-line. You will also need a working Platform SDK for Windows that is available for free from Microsoft.
The projects/makefiles will generate automatically some source files needed to compile GStreamer. That requires that you have installed on your system some GNU tools and that they are available in your system PATH.
The GStreamer project depends on other libraries, namely :
GNU tools needed that you can find on http://gnuwin32.sourceforge.net/
the generated files from the -auto makefiles will be available soon separately on the net for convenience (people who don't want to install GNU tools).