Address some issues with detecting the architecture. See...

tools/utils.py

 # Copyright 2008 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 45 matching lines @@
   elif id == 'FreeBSD':
     return 'freebsd'
   elif id == 'OpenBSD':
     return 'openbsd'
   elif id == 'SunOS':
     return 'solaris'
   else:
     return None
 
 
+# This will default to building the 32 bit VM even on machines that are capable
+# of running the 64 bit VM.  Use the scons option --arch=x64 to force it to build
+# the 64 bit VM.
 def GuessArchitecture():
   id = platform.machine()
+  id = id.lower()  # Windows 7 capitalizes 'AMD64'.
   if id.startswith('arm'):
     return 'arm'
-  elif (not id) or (not re.match('(x|i[3-6])86', id) is None):
+  elif (not id) or (not re.match('(x|i[3-6])86$', id) is None):
     return 'ia32'
   elif id == 'i86pc':
     return 'ia32'
+  elif id == 'x86_64':
+    return 'ia32'
   elif id == 'amd64':
     return 'ia32'
   else:
     return None
 
 
 def GuessWordsize():
   if '64' in platform.machine():
     return '64'
   else:
     return '32'
 
 
 def IsWindows():
   return GuessOS() == 'win32'