Hacked 'set_final_options()' to set (hopefully) appropriate values for
'install_site_lib' and install_site_platlib' on non-POSIX platforms.
Should at least work for NT, as this is adopted from Amos Latteier's NT
patches.  Also added extensive comments bitching about the inadequacy of
the current model, both under POSIX and NT (and probably other) systems.
diff --git a/Lib/distutils/command/install.py b/Lib/distutils/command/install.py
index ec73b1c..54b8187 100644
--- a/Lib/distutils/command/install.py
+++ b/Lib/distutils/command/install.py
@@ -48,6 +48,7 @@
                ('optimize-py', None, "compile .py to .pyo (optimized)"),
               ]
 
+
     def set_default_options (self):
 
         self.build_base = None
@@ -83,6 +84,29 @@
 
     def set_final_options (self):
 
+        # XXX this method is where the default installation directories
+        # for modules and extension modules are determined.  (Someday,
+        # the default installation directories for scripts,
+        # documentation, and whatever else the Distutils can build and
+        # install will also be determined here.)  Thus, this is a pretty
+        # important place to fiddle with for anyone interested in
+        # installation schemes for the Python library.  Issues that
+        # are not yet resolved to my satisfaction:
+        #   * how much platform dependence should be here, and
+        #     how much can be pushed off to sysconfig (or, better, the
+        #     Makefiles parsed by sysconfig)?
+        #   * how independent of Python version should this be -- ie.
+        #     should we have special cases to handle Python 1.5 and
+        #     older, and then do it "the right way" for 1.6?  Or should
+        #     we install a site.py along with Distutils under pre-1.6
+        #     Python to take care of the current deficiencies in
+        #     Python's library installation scheme?
+        #
+        # Currently, this method has hacks to distinguish POSIX from
+        # non-POSIX systems (for installation of site-local modules),
+        # and assumes the Python 1.5 installation tree with no site.py
+        # to fix things.
+
         # Figure out the build directories, ie. where to install from
         self.set_peer_option ('build', 'basedir', self.build_base)
         self.set_undefined_options ('build',
@@ -114,15 +138,37 @@
             self.install_platlib = \
                 self.replace_sys_prefix ('BINLIBDEST', ('lib','python1.5'), 1)
 
+
+        # Here is where we decide where to install most library files:
+        # on POSIX systems, they go to 'site-packages' under the
+        # install_lib (determined above -- typically
+        # /usr/local/lib/python1.x).  Unfortunately, both
+        # platform-independent (.py*) and platform-specific (.so) files
+        # go to this directory, since there is no site-packages under
+        # $exec_prefix in the usual way that Python builds sys.path.  On
+        # non-POSIX systems, the situation is even worse: everything
+        # gets dumped right into $exec_prefix, not even a lib
+        # subdirectory!  But apparently that's what needs to be done to
+        # make it work under Python 1.5 -- hope we can get this fixed
+        # for 1.6!
+
         if self.install_site_lib is None:
-            self.install_site_lib = \
-                os.path.join (self.install_lib, 'site-packages')
+            if os.name == 'posix':
+                self.install_site_lib = \
+                    os.path.join (self.install_lib, 'site-packages')
+            else:
+                self.install_site_lib = self.exec_prefix
+
         if self.install_site_platlib is None:
-            # XXX ugh! this puts platform-specific files in with shared files,
-            # with no nice way to override it! (this might be a Python
-            # problem, though, not a Distutils problem...)
-            self.install_site_platlib = \
-                os.path.join (self.install_lib, 'site-packages')
+            if os.name == 'posix':
+                # XXX ugh! this puts platform-specific files in with
+                # shared files, with no nice way to override it! (this
+                # might be a Python problem, though, not a Distutils
+                # problem...)
+                self.install_site_platlib = \
+                    os.path.join (self.install_lib, 'site-packages')
+            else:
+                self.install_site_platlib = self.exec_prefix
 
         #if self.install_scheme == 'site':
         #    install_lib = self.install_site_lib
@@ -181,6 +227,9 @@
 
         self.set_final_options ()
 
+        # Obviously have to build before we can install
+        self.run_peer ('build')
+
         # Install modules in two steps: "platform-shared" files (ie. pure
         # python modules) and platform-specific files (compiled C
         # extensions).