We thank Jared Davis for providing the following instructions for ACL2
Version  2.8, which we include verbatim and expect apply to future
versions.
	      Building ACL2 on Windows from Scratch
   _____________________________________________________________
   Note: The disk space requirements are large.  Not including
   emacs, I had about 275 MB taken up by msys/mingw32/gcl/acl2
   during the build process.  You can probably use much less
   space by removing files after you use them, but I didn't
   bother to do that.
   Here are the steps I took:
   Downloaded emacs 21.3 full distribution and installed
   Downloaded msys 1.10.10, installed to c:\acl2
   Downloaded mingw 3.1.0-1, installed to c:\acl2\mingw
   Downloaded gcl 2.5.3, extracted to c:\acl2\mingw
   Downloaded acl2 2.8, extracted to c:\acl2\sources
   Compiling gcl:
     in msys:
       cd /acl2/ming2/gcl-2.5.3
       ./configure
       make
       make install
   Compiling acl2:
     copy "etags.exe" to /mingw/bin.  you can find this program
     in your emacs folder, under "bin".
     in msys:
       cd /sources
       make
   Certifying ACL2 books:
   This took 111 minutes on my Athlon 2500+
     in msys:
       cd /sources
       mv nsaved_acl2.gcl.exe saved_acl2.exe
       vim books/Makefile-generic, remove "nice" from this line:
	   ACL2=time nice ../../saved_acl2
       make certify-books ACL2=/sources/saved_acl2.exe