All of Amber (except for pmemd, but including the X-windows parts) will compile and run on Windows using the Cygwin development tools: see http://www.cygwin.com. The cygwin package provides a way to make Microsoft Windows machines resemble a Linux/Unix environment; if you are unfamiliar with the Linux/Unix environment, you will need to learn at least the basics of that in order to use Amber on Windows.
You will also need to obtain a Fortran 90 compiler (for sander and nmode) because one is not distributed with cygwin. Both g95 or gfortran will work, although g95 is the one we have the most experience with.
Note that Cygwin provides a POSIX-compatible environment for Windows. Effective use of this environment requires a basic familiarity with the principles of Linux or Unix operating systems. Building the Windows version is thus somewhat more complex (not simpler) than building under other operating systems. The Windows version has primarily been used in serial (single-cpu) mode; it will work with the LAM libraries supplied with Amber10, or with MPICH2 libraries. For long-running jobs, Windows can have an annoying habit of giving lots (or all) of the CPU time to an interactive process, so that background processes suffer.
The bottom line is that the Windows version is functional, but the primary development and target operating system is Unix or Linux.