diff --git a/setup_native/source/win32/customactions/reg4allmsdoc/exports.dxp b/setup_native/source/win32/customactions/reg4allmsdoc/exports.dxp
index 566981ba569e..54ebb2f675f4 100644
--- a/setup_native/source/win32/customactions/reg4allmsdoc/exports.dxp
+++ b/setup_native/source/win32/customactions/reg4allmsdoc/exports.dxp
@@ -1,3 +1,4 @@
 FindRegisteredExtensions
 LookForRegisteredExtensions
-RegisterSomeExtensions
\ No newline at end of file
+RegisterSomeExtensions
+RestoreRegAllMSDoc
diff --git a/setup_native/source/win32/customactions/reg4allmsdoc/reg4allmsi.cxx b/setup_native/source/win32/customactions/reg4allmsdoc/reg4allmsi.cxx
index 54a40cd08d8f..7b9cfc992245 100644
--- a/setup_native/source/win32/customactions/reg4allmsdoc/reg4allmsi.cxx
+++ b/setup_native/source/win32/customactions/reg4allmsdoc/reg4allmsi.cxx
@@ -213,6 +213,9 @@ static LONG DeleteSubKeyTree( HKEY RootKey, LPCSTR lpKey )
     return rc;
 }
 
+// Unused
+#if 0
+
 //----------------------------------------------------------
 static BOOL RemoveExtensionInRegistry( LPCSTR lpSubKey )
 {
@@ -263,6 +266,8 @@ static BOOL RemoveExtensionInRegistry( LPCSTR lpSubKey )
     return ( ERROR_SUCCESS == lResult );
 }
 
+#endif
+
 //----------------------------------------------------------
 bool GetMsiProp( MSIHANDLE handle, LPCSTR name, /*out*/std::string& value )
 {
@@ -306,12 +311,60 @@ static void registerForExtension( MSIHANDLE handle, const int nIndex, bool bRegi
     }
 }
 
+//----------------------------------------------------------
+static void saveOldRegistration( LPCSTR lpSubKey )
+{
+    BOOL    bRet = false;
+    HKEY    hKey = NULL;
+    LONG    lResult = RegOpenKeyExA( HKEY_CLASSES_ROOT, lpSubKey, 0,
+                                     KEY_QUERY_VALUE|KEY_SET_VALUE, &hKey );
+
+    if ( ERROR_SUCCESS == lResult )
+    {
+        CHAR    szBuffer[1024];
+        DWORD   nSize = sizeof( szBuffer );
+
+        lResult = RegQueryValueExA( hKey, "", NULL, NULL, (LPBYTE)szBuffer, &nSize );
+        if ( ERROR_SUCCESS == lResult )
+        {
+            szBuffer[nSize] = '\0';
+
+            // No need to save assocations for our own types
+            if ( strncmp( szBuffer, "OpenOffice.org.", 15 ) != 0 )
+            {
+                // Save the old association
+                RegSetValueExA( hKey, "OOoBackupAssociation", 0,
+                                REG_SZ, (LPBYTE)szBuffer, nSize );
+                // Also save what the old association means, just so we can try to verify
+                // if/when restoring it that the old application still exists
+                HKEY hKey2 = NULL;
+                lResult = RegOpenKeyExA( HKEY_CLASSES_ROOT, szBuffer, 0,
+                                         KEY_QUERY_VALUE, &hKey2 );
+                if ( ERROR_SUCCESS == lResult )
+                {
+                    nSize = sizeof( szBuffer );
+                    lResult = RegQueryValueExA( hKey2, "", NULL, NULL, (LPBYTE)szBuffer, &nSize );
+                    if ( ERROR_SUCCESS == lResult )
+                    {
+                        RegSetValueExA( hKey, "OOoBackupAssociationDeref", 0,
+                                        REG_SZ, (LPBYTE)szBuffer, nSize );
+                    }
+                    RegCloseKey( hKey2 );
+                }
+            }
+        }
+        RegCloseKey( hKey );
+    }
+}
+
 //----------------------------------------------------------
 static void registerForExtensions( MSIHANDLE handle, BOOL bRegisterAll )
 { // Check all file extensions
     int nIndex = 0;
     while ( g_Extensions[nIndex] != 0 )
     {
+        saveOldRegistration( g_Extensions[nIndex] );
+
         BOOL bRegister = bRegisterAll || CheckExtensionInRegistry( g_Extensions[nIndex] );
         if ( bRegister )
             registerForExtension( handle, nIndex, true );
@@ -478,6 +531,10 @@ extern "C" UINT __stdcall RegisterSomeExtensions( MSIHANDLE handle )
 }
 
 //----------------------------------------------------------
+//
+// This is the (slightly misleadinly named) entry point for the
+// custom action called Regallmsdocdll.
+//
 extern "C" UINT __stdcall FindRegisteredExtensions( MSIHANDLE handle )
 {
     if ( IsSetMsiProp( handle, "FILETYPEDIALOGUSED" ) )
@@ -514,7 +571,12 @@ extern "C" UINT __stdcall FindRegisteredExtensions( MSIHANDLE handle )
     return ERROR_SUCCESS;
 }
 
+#if 0
+
 //----------------------------------------------------------
+//
+// This entry is not called for any custom action.
+//
 extern "C" UINT __stdcall DeleteRegisteredExtensions( MSIHANDLE /*handle*/ )
 {
     OutputDebugStringFormat( "DeleteRegisteredExtensions\n" );
@@ -530,4 +592,78 @@ extern "C" UINT __stdcall DeleteRegisteredExtensions( MSIHANDLE /*handle*/ )
     return ERROR_SUCCESS;
 }
 
+#endif
+
+//----------------------------------------------------------
+static void restoreOldRegistration( LPCSTR lpSubKey )
+{
+    BOOL    bRet = false;
+    HKEY    hKey = NULL;
+    LONG    lResult = RegOpenKeyExA( HKEY_CLASSES_ROOT, lpSubKey, 0,
+                                     KEY_QUERY_VALUE|KEY_SET_VALUE, &hKey );
+
+    if ( ERROR_SUCCESS == lResult )
+    {
+        CHAR    szBuffer[1024];
+        DWORD   nSize = sizeof( szBuffer );
+
+        lResult = RegQueryValueExA( hKey, "OOoBackupAssociation", NULL, NULL,
+                                    (LPBYTE)szBuffer, &nSize );
+        if ( ERROR_SUCCESS == lResult )
+        {
+            HKEY hKey2 = NULL;
+            lResult = RegOpenKeyExA( HKEY_CLASSES_ROOT, szBuffer, 0,
+                                     KEY_QUERY_VALUE, &hKey2 );
+            if ( ERROR_SUCCESS == lResult )
+            {
+                CHAR   szBuffer2[1024];
+                DWORD  nSize2 = sizeof( szBuffer2 );
+
+                lResult = RegQueryValueExA( hKey2, "", NULL, NULL, (LPBYTE)szBuffer2, &nSize2 );
+                if ( ERROR_SUCCESS == lResult )
+                {
+                    CHAR   szBuffer3[1024];
+                    DWORD  nSize3 = sizeof( szBuffer3 );
+
+                    // Try to verify that the old association is OK to restore
+                    lResult = RegQueryValueExA( hKey, "OOoBackupAssociationDeref", NULL, NULL,
+                                                (LPBYTE)szBuffer3, &nSize3 );
+                    if ( ERROR_SUCCESS == lResult )
+                    {
+                        if ( nSize2 == nSize3 && strcmp (szBuffer2, szBuffer3) == 0)
+                        {
+                            // Yep. So restore it
+                            RegSetValueExA( hKey, "", 0, REG_SZ, (LPBYTE)szBuffer, nSize );
+                        }
+                    }
+                }
+                RegCloseKey( hKey2 );
+            }
+            RegDeleteValueA( hKey, "OOoBackupAssociation" );
+        }
+        RegDeleteValueA( hKey, "OOoBackupAssociationDeref" );
+        RegCloseKey( hKey );
+    }
+}
+
+//----------------------------------------------------------
+//
+// This function is not in OO.o. We call this from the
+// Restoreregallmsdocdll custom action.
+//
+extern "C" UINT __stdcall RestoreRegAllMSDoc( MSIHANDLE /*handle*/ )
+{
+    OutputDebugStringFormat( "RestoreRegAllMSDoc\n" );
+
+    int nIndex = 0;
+    while ( g_Extensions[nIndex] != 0 )
+    {
+        restoreOldRegistration( g_Extensions[nIndex] );
+        ++nIndex;
+    }
+
+
+    return ERROR_SUCCESS;
+}
+
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */