To compile Emacs on Windows, you will need the MingW or Cygwin port of GCC with MingW make, or a Microsoft C compiler with nmake and the single threaded C runtime library. Recent versions of Microsoft Visual Studio no longer come with the single threaded C runtime library, which is required for certain POSIX compatibility, so MingW is usually the best choice. Image support requires external libraries, the headers and import libraries for which will need to be installed where your compiler can find them. You will also need ports of GNU rm and cp, as the Windows native equivalents are not consistent between versions. GNU texinfo will be required to build the manuals. See Other useful ports.
After unpacking the source, or checking out of Bzr, be sure to read the instructions in nt/README and nt/INSTALL.