diff --git a/PC/dl_nt.c b/PC/dl_nt.c
--- a/PC/dl_nt.c
+++ b/PC/dl_nt.c
@@ -18,7 +18,8 @@
 HMODULE PyWin_DLLhModule = NULL;
 const char *PyWin_DLLVersionString = dllVersionBuffer;
 
-// Windows "Activation Context" work:
+#if HAVE_SXS
+// Windows "Activation Context" work.
 // Our .pyd extension modules are generally built without a manifest (ie,
 // those included with Python and those built with a default distutils.
 // This requires we perform some "activation context" magic when loading our
@@ -29,6 +30,8 @@
 // As an added complication, this magic only works on XP or later - we simply
 // use the existence (or not) of the relevant function pointers from kernel32.
 // See bug 4566 (http://python.org/sf/4566) for more details.
+// In Visual Studio 2010, side by side assemblies are no longer used by
+// default.
 
 typedef BOOL (WINAPI * PFN_GETCURRENTACTCTX)(HANDLE *);
 typedef BOOL (WINAPI * PFN_ACTIVATEACTCTX)(HANDLE, ULONG_PTR *);
@@ -75,6 +78,7 @@
         if (!(*pfnDeactivateActCtx)(0, cookie))
             OutputDebugString("Python failed to de-activate the activation context\n");
 }
+#endif /* HAVE_SXS */
 
 BOOL    WINAPI  DllMain (HANDLE hInst,
                                                 ULONG ul_reason_for_call,
@@ -87,17 +91,21 @@
             // 1000 is a magic number I picked out of the air.  Could do with a #define, I spose...
             LoadString(hInst, 1000, dllVersionBuffer, sizeof(dllVersionBuffer));
 
+#if HAVE_SXS
             // and capture our activation context for use when loading extensions.
             _LoadActCtxPointers();
             if (pfnGetCurrentActCtx && pfnAddRefActCtx)
                 if ((*pfnGetCurrentActCtx)(&PyWin_DLLhActivationContext))
                     if (!(*pfnAddRefActCtx)(PyWin_DLLhActivationContext))
                         OutputDebugString("Python failed to load the default activation context\n");
+#endif
             break;
 
         case DLL_PROCESS_DETACH:
+#if HAVE_SXS
             if (pfnReleaseActCtx)
                 (*pfnReleaseActCtx)(PyWin_DLLhActivationContext);
+#endif
             break;
     }
     return TRUE;
diff --git a/PC/msvcrtmodule.c b/PC/msvcrtmodule.c
--- a/PC/msvcrtmodule.c
+++ b/PC/msvcrtmodule.c
@@ -494,6 +494,7 @@
 #endif
 
     /* constants for the crt versions */
+    (void)st;
 #ifdef _VC_ASSEMBLY_PUBLICKEYTOKEN
     st = PyModule_AddStringConstant(m, "VC_ASSEMBLY_PUBLICKEYTOKEN",
                                     _VC_ASSEMBLY_PUBLICKEYTOKEN);
diff --git a/PC/pyconfig.h b/PC/pyconfig.h
--- a/PC/pyconfig.h
+++ b/PC/pyconfig.h
@@ -215,14 +215,19 @@
 #define copysign _copysign
 #define hypot _hypot
 
-#endif /* _MSC_VER */
+/* Side by Side assemblies supported in VS 2005 and VS 2008 but not 2010*/
+#if _MSC_VER >= 1400 && _MSC_VER < 1600
+#define HAVE_SXS 1
+#endif
 
 /* define some ANSI types that are not defined in earlier Win headers */
-#if defined(_MSC_VER) && _MSC_VER >= 1200
+#if _MSC_VER >= 1200
 /* This file only exists in VC 6.0 or higher */
 #include <basetsd.h>
 #endif
 
+#endif /* _MSC_VER */
+
 /* ------------------------------------------------------------------------*/
 /* The Borland compiler defines __BORLANDC__ */
 /* XXX These defines are likely incomplete, but should be easy to fix. */
diff --git a/Python/dynload_win.c b/Python/dynload_win.c
--- a/Python/dynload_win.c
+++ b/Python/dynload_win.c
@@ -12,8 +12,10 @@
 #include <windows.h>
 
 // "activation context" magic - see dl_nt.c...
+#if HAVE_SXS
 extern ULONG_PTR _Py_ActivateActCtx();
 void _Py_DeactivateActCtx(ULONG_PTR cookie);
+#endif
 
 const struct filedescr _PyImport_DynLoadFiletab[] = {
 #ifdef _DEBUG
@@ -191,18 +193,24 @@
     {
         HINSTANCE hDLL = NULL;
         unsigned int old_mode;
+#if HAVE_SXS
         ULONG_PTR cookie = 0;
+#endif
 
         /* Don't display a message box when Python can't load a DLL */
         old_mode = SetErrorMode(SEM_FAILCRITICALERRORS);
 
+#if HAVE_SXS
         cookie = _Py_ActivateActCtx();
+#endif
         /* We use LoadLibraryEx so Windows looks for dependent DLLs
             in directory of pathname first. */
         /* XXX This call doesn't exist in Windows CE */
         hDLL = LoadLibraryExW(wpathname, NULL,
                               LOAD_WITH_ALTERED_SEARCH_PATH);
+#if HAVE_SXS
         _Py_DeactivateActCtx(cookie);
+#endif
 
         /* restore old error mode settings */
         SetErrorMode(old_mode);