The officially supported build environment for monotone on Windows is MinGW. The exact requirements are listed in the specific page.

Building monotone under Cygwin is also known to work. monotone is also included as a package in all Cygwin mirrors and can be easily installed using Cygwin's setup.exe.

Building with Microsoft Services For Unix is untested, but would probably work without too much difficulty.

Support for building using Visual Studio 8 is available, but we don't have a VC8 buildbot so sometimes the build is broken.