diff --git a/tools/utils.py b/tools/utils.py
index 3a55722e66..8083091b6d 100644
--- a/tools/utils.py
+++ b/tools/utils.py
@@ -63,14 +63,20 @@ def GuessOS():
     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: