diff --git a/allmakefiles.sh b/allmakefiles.sh
index 09161e50a0c..54023a6feeb 100755
--- a/allmakefiles.sh
+++ b/allmakefiles.sh
@@ -30,6 +30,7 @@ build/Makefile
 build/pgo/Makefile
 build/pgo/blueprint/Makefile
 build/pgo/js-input/Makefile
+build/virtualenv/Makefile
 config/Makefile
 config/autoconf.mk
 config/nspr/Makefile
diff --git a/build/virtualenv/Makefile.in b/build/virtualenv/Makefile.in
new file mode 100644
index 00000000000..d050eaf7e97
--- /dev/null
+++ b/build/virtualenv/Makefile.in
@@ -0,0 +1,15 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DEPTH		= ../..
+topsrcdir	= @top_srcdir@
+srcdir		= @srcdir@
+VPATH		= @srcdir@
+
+include $(DEPTH)/config/autoconf.mk
+
+default::
+# install some packages
+
+include $(topsrcdir)/config/rules.mk
diff --git a/configure.in b/configure.in
index 45aad803396..8a63cc51ebb 100644
--- a/configure.in
+++ b/configure.in
@@ -7921,10 +7921,9 @@ else
     fi
     AC_SUBST(CL_INCLUDES_PREFIX)
     rm -f dummy-hello.c
-    _topsrcdirwin=`cd \`dirname $0\`; pwd -W`
     dnl cl.py provides dependency generation for MSVC
-    CC_WRAPPER="$PYTHON -O $_topsrcdirwin/build/cl.py"
-    CXX_WRAPPER="$PYTHON -O $_topsrcdirwin/build/cl.py"
+    CC_WRAPPER='$(PYTHON) -O $(topsrcdir)/build/cl.py'
+    CXX_WRAPPER='$(PYTHON) -O $(topsrcdir)/build/cl.py'
     COMPILER_DEPEND=1
   fi
 fi
@@ -8566,7 +8565,6 @@ AC_SUBST(MOZ_MAPINFO)
 AC_SUBST(MOZ_BROWSE_INFO)
 AC_SUBST(MOZ_TOOLS_DIR)
 AC_SUBST(WIN32_REDIST_DIR)
-AC_SUBST(PYTHON)
 AC_SUBST(MAKENSISU)
 
 dnl Echo the CFLAGS to remove extra whitespace.
@@ -8948,6 +8946,22 @@ AC_SUBST(MOZ_DEFINES)
 rm -f confdefs.h
 mv confdefs.h.save confdefs.h
 
+dnl Create a virtualenv where we can install local Python packages
+AC_MSG_RESULT([Creating Python virtualenv])
+rm -rf _virtualenv
+mkdir -p _virtualenv
+$PYTHON $_topsrcdir/other-licenses/virtualenv/virtualenv.py ./_virtualenv
+case "$host_os" in
+mingw*)
+    PYTHON=`pwd`/_virtualenv/Scripts/python.exe
+    ;;
+*)
+    PYTHON=`pwd`/_virtualenv/bin/python
+    ;;
+esac
+
+AC_SUBST(PYTHON)
+
 dnl Load the list of Makefiles to generate.
 dnl   To add new Makefiles, edit allmakefiles.sh.
 dnl   allmakefiles.sh sets the variable, MAKEFILES.
@@ -8971,6 +8985,10 @@ mv -f config/autoconf.mk config/autoconf.mk.orig 2> /dev/null
 
 AC_OUTPUT($MAKEFILES)
 
+# Populate the virtualenv
+AC_MSG_RESULT([Populating Python virtualenv])
+$MAKE -C build/virtualenv || exit 1
+
 # Generate a JSON config file for unittest harnesses etc to read
 # build configuration details from in a standardized way.
 OS_TARGET=${OS_TARGET} TARGET_CPU=${TARGET_CPU} MOZ_DEBUG=${MOZ_DEBUG} \
diff --git a/toolkit/crashreporter/tools/symbolstore.py b/toolkit/crashreporter/tools/symbolstore.py
index 286089e81f6..9d2b705bf37 100755
--- a/toolkit/crashreporter/tools/symbolstore.py
+++ b/toolkit/crashreporter/tools/symbolstore.py
@@ -352,7 +352,10 @@ def GetVCSFilename(file, srcdirs):
 def GetPlatformSpecificDumper(**kwargs):
     """This function simply returns a instance of a subclass of Dumper
     that is appropriate for the current platform."""
+    # Python 2.5 has a bug where platform.system() returns 'Microsoft'.
+    # Remove this when we no longer support Python 2.5.
     return {'Windows': Dumper_Win32,
+            'Microsoft': Dumper_Win32,
             'Linux': Dumper_Linux,
             'Sunos5': Dumper_Solaris,
             'Darwin': Dumper_Mac}[platform.system()](**kwargs)