Use GS- and bufferoverlowU.lib where appropriate, for AMD64.
diff --git a/PCbuild/_bsddb.vcproj b/PCbuild/_bsddb.vcproj
index 581c3fc..4a612a4 100644
--- a/PCbuild/_bsddb.vcproj
+++ b/PCbuild/_bsddb.vcproj
@@ -192,7 +192,7 @@
 			ATLMinimizesCRunTimeLibraryUsage="FALSE">
 			<Tool
 				Name="VCCLCompilerTool"
-				AdditionalOptions=" /USECL:MS_OPTERON"
+				AdditionalOptions=" /USECL:MS_OPTERON /GS-"
 				Optimization="2"
 				InlineFunctionExpansion="1"
 				AdditionalIncludeDirectories="..\Include;..\PC;&quot;..\..\db-4.4.20\build_win32&quot;"
diff --git a/PCbuild/_elementtree.vcproj b/PCbuild/_elementtree.vcproj
index 3278874..dec48e3 100644
--- a/PCbuild/_elementtree.vcproj
+++ b/PCbuild/_elementtree.vcproj
@@ -190,7 +190,7 @@
 			ATLMinimizesCRunTimeLibraryUsage="FALSE">
 			<Tool
 				Name="VCCLCompilerTool"
-				AdditionalOptions=" /USECL:MS_OPTERON"
+				AdditionalOptions=" /USECL:MS_OPTERON /GS-"
 				Optimization="2"
 				InlineFunctionExpansion="1"
 				AdditionalIncludeDirectories="..\Include,..\PC,..\Modules\expat"
diff --git a/PCbuild/_msi.vcproj b/PCbuild/_msi.vcproj
index 503c174..fb8925e 100644
--- a/PCbuild/_msi.vcproj
+++ b/PCbuild/_msi.vcproj
@@ -189,7 +189,7 @@
 			CharacterSet="2">
 			<Tool
 				Name="VCCLCompilerTool"
-				AdditionalOptions=" /USECL:MS_OPTERON"
+				AdditionalOptions=" /USECL:MS_OPTERON /GS-"
 				Optimization="2"
 				InlineFunctionExpansion="1"
 				AdditionalIncludeDirectories="..\Include,..\PC"
@@ -210,7 +210,7 @@
 			<Tool
 				Name="VCLinkerTool"
 				AdditionalOptions=" /MACHINE:AMD64 /USELINK:MS_SDK"
-				AdditionalDependencies="fci.lib msi.lib rpcrt4.lib"
+				AdditionalDependencies="fci.lib msi.lib rpcrt4.lib bufferoverflowU.lib"
 				OutputFile="./_msi.pyd"
 				LinkIncremental="1"
 				SuppressStartupBanner="TRUE"
diff --git a/PCbuild/_socket.vcproj b/PCbuild/_socket.vcproj
index bdfc9d9..22fb492 100644
--- a/PCbuild/_socket.vcproj
+++ b/PCbuild/_socket.vcproj
@@ -189,7 +189,7 @@
 			ATLMinimizesCRunTimeLibraryUsage="FALSE">
 			<Tool
 				Name="VCCLCompilerTool"
-				AdditionalOptions=" /USECL:MS_OPTERON"
+				AdditionalOptions=" /USECL:MS_OPTERON /GS-"
 				Optimization="2"
 				InlineFunctionExpansion="1"
 				AdditionalIncludeDirectories="..\Include,..\PC"
diff --git a/PCbuild/_testcapi.vcproj b/PCbuild/_testcapi.vcproj
index f286a30..c58331e 100644
--- a/PCbuild/_testcapi.vcproj
+++ b/PCbuild/_testcapi.vcproj
@@ -185,7 +185,7 @@
 			CharacterSet="2">
 			<Tool
 				Name="VCCLCompilerTool"
-				AdditionalOptions=" /USECL:MS_OPTERON"
+				AdditionalOptions=" /USECL:MS_OPTERON /GS-"
 				Optimization="2"
 				InlineFunctionExpansion="1"
 				AdditionalIncludeDirectories="..\Include,..\PC"
diff --git a/PCbuild/_tkinter.vcproj b/PCbuild/_tkinter.vcproj
index 57b7606..4ffeae5 100644
--- a/PCbuild/_tkinter.vcproj
+++ b/PCbuild/_tkinter.vcproj
@@ -192,7 +192,7 @@
 			ATLMinimizesCRunTimeLibraryUsage="FALSE">
 			<Tool
 				Name="VCCLCompilerTool"
-				AdditionalOptions=" /USECL:MS_OPTERON"
+				AdditionalOptions=" /USECL:MS_OPTERON /GS-"
 				Optimization="2"
 				InlineFunctionExpansion="1"
 				AdditionalIncludeDirectories="..\..\tcltk\include,..\Include,..\PC"
diff --git a/PCbuild/bz2.vcproj b/PCbuild/bz2.vcproj
index 841e94d..8cbe15a 100644
--- a/PCbuild/bz2.vcproj
+++ b/PCbuild/bz2.vcproj
@@ -202,7 +202,7 @@
 			ATLMinimizesCRunTimeLibraryUsage="FALSE">
 			<Tool
 				Name="VCCLCompilerTool"
-				AdditionalOptions=" /USECL:MS_OPTERON"
+				AdditionalOptions=" /USECL:MS_OPTERON /GS-"
 				Optimization="2"
 				InlineFunctionExpansion="1"
 				AdditionalIncludeDirectories="..\Include,..\PC,..\..\bzip2-1.0.3"
diff --git a/PCbuild/pythoncore.vcproj b/PCbuild/pythoncore.vcproj
index 910dbb1..5f39a17 100644
--- a/PCbuild/pythoncore.vcproj
+++ b/PCbuild/pythoncore.vcproj
@@ -211,7 +211,7 @@
 			ATLMinimizesCRunTimeLibraryUsage="FALSE">
 			<Tool
 				Name="VCCLCompilerTool"
-				AdditionalOptions="/Zm200  /USECL:MS_OPTERON"
+				AdditionalOptions="/Zm200  /USECL:MS_OPTERON /GS-"
 				Optimization="2"
 				InlineFunctionExpansion="1"
 				AdditionalIncludeDirectories="..\Include,..\PC"
diff --git a/PCbuild/unicodedata.vcproj b/PCbuild/unicodedata.vcproj
index e48e535..472b6b7 100644
--- a/PCbuild/unicodedata.vcproj
+++ b/PCbuild/unicodedata.vcproj
@@ -185,7 +185,7 @@
 			CharacterSet="2">
 			<Tool
 				Name="VCCLCompilerTool"
-				AdditionalOptions=" /USECL:MS_OPTERON"
+				AdditionalOptions=" /USECL:MS_OPTERON /GS-"
 				Optimization="2"
 				InlineFunctionExpansion="1"
 				AdditionalIncludeDirectories="..\Include,..\PC"
diff --git a/PCbuild/winsound.vcproj b/PCbuild/winsound.vcproj
index b645a24..34aadbf 100644
--- a/PCbuild/winsound.vcproj
+++ b/PCbuild/winsound.vcproj
@@ -188,7 +188,7 @@
 			CharacterSet="2">
 			<Tool
 				Name="VCCLCompilerTool"
-				AdditionalOptions=" /USECL:MS_OPTERON"
+				AdditionalOptions=" /USECL:MS_OPTERON /GS-"
 				Optimization="2"
 				InlineFunctionExpansion="1"
 				AdditionalIncludeDirectories="..\Include,..\PC"