As best as I can tell, the Windows version doesn't exist anymore. Maybe whoever was maintaining it before had to stop for some reason.
I wonder what it takes to compile a PECL extension under Windows.
Edit
Here's some info on compiling a different PECL extension on Windows. You may be able to extrapolate to the inclued extension.
Edit
WAMP Server comes with PECL & PEAR. I can actually run the command pecl install inclued-alpha from the Windows command-line and it goes out and tries to grab the inclued extension from the PECL site.
Unfortunately it dies when it unpacks the .tgz file and tries to compile it
ERROR: The DSP inclued.dsp does not exist.