diff --git a/xpfe/bootstrap/macbuild/Contents/Info.plist.in b/xpfe/bootstrap/macbuild/Contents/Info.plist.in
index 53f0c9ccee22..f9f675286e8b 100644
--- a/xpfe/bootstrap/macbuild/Contents/Info.plist.in
+++ b/xpfe/bootstrap/macbuild/Contents/Info.plist.in
@@ -183,7 +183,6 @@
 					<string>jpe</string>
 					<string>png</string>
 					<string>gif</string>
-					<string>mng</string>
 					<string>bmp</string>
 					<string>ico</string>
 					<string>xbm</string>
diff --git a/xpfe/bootstrap/nsNativeAppSupportWin.cpp b/xpfe/bootstrap/nsNativeAppSupportWin.cpp
index 190c7e52a3a3..faaaa33a5daf 100644
--- a/xpfe/bootstrap/nsNativeAppSupportWin.cpp
+++ b/xpfe/bootstrap/nsNativeAppSupportWin.cpp
@@ -1188,7 +1188,6 @@ static PRBool handlingHTTP() {
                 settings->SetIsHandlingJPEG( PR_FALSE );
                 settings->SetIsHandlingGIF( PR_FALSE );
                 settings->SetIsHandlingPNG( PR_FALSE );
-                settings->SetIsHandlingMNG( PR_FALSE );
                 settings->SetIsHandlingBMP( PR_FALSE );
                 settings->SetIsHandlingICO( PR_FALSE );
                 settings->SetIsHandlingXML( PR_FALSE );
diff --git a/xpfe/components/winhooks/nsIWindowsHooks.idl b/xpfe/components/winhooks/nsIWindowsHooks.idl
index 7fe28364fa53..01e49597ee54 100644
--- a/xpfe/components/winhooks/nsIWindowsHooks.idl
+++ b/xpfe/components/winhooks/nsIWindowsHooks.idl
@@ -118,7 +118,7 @@ interface nsIDOMElement;
  * for historical reasons (it corresponds to the internal Prefs struct
  * that was in nsIDefaultBrowser.h in Mozilla Classic).
  */
-[scriptable, uuid(4ce9aa90-0a6a-11d4-8076-00600811a9c3)]
+[scriptable, uuid(d7a33e08-705e-4506-aba0-843c73dfd304)]
 interface nsIWindowsHooksSettings : nsISupports {
 
     // Internet shortcuts (based on "protocol").
@@ -133,7 +133,6 @@ interface nsIWindowsHooksSettings : nsISupports {
     attribute boolean isHandlingJPEG;
     attribute boolean isHandlingGIF;
     attribute boolean isHandlingPNG;
-    attribute boolean isHandlingMNG;
     attribute boolean isHandlingXBM;
     attribute boolean isHandlingBMP;
     attribute boolean isHandlingICO;
diff --git a/xpfe/components/winhooks/nsWindowsHooks.cpp b/xpfe/components/winhooks/nsWindowsHooks.cpp
index 92c20fc4cc3e..31b0923b623e 100644
--- a/xpfe/components/winhooks/nsWindowsHooks.cpp
+++ b/xpfe/components/winhooks/nsWindowsHooks.cpp
@@ -128,7 +128,6 @@ DEFINE_GETTER_AND_SETTER( IsHandlingHTML,   mHandleHTML   )
 DEFINE_GETTER_AND_SETTER( IsHandlingJPEG,   mHandleJPEG   )
 DEFINE_GETTER_AND_SETTER( IsHandlingGIF,    mHandleGIF    )
 DEFINE_GETTER_AND_SETTER( IsHandlingPNG,    mHandlePNG    )
-DEFINE_GETTER_AND_SETTER( IsHandlingMNG,    mHandleMNG    )
 DEFINE_GETTER_AND_SETTER( IsHandlingXBM,    mHandleXBM    )
 DEFINE_GETTER_AND_SETTER( IsHandlingBMP,    mHandleBMP    )
 DEFINE_GETTER_AND_SETTER( IsHandlingICO,    mHandleICO    )
@@ -151,7 +150,6 @@ NS_IMPL_ISUPPORTS1( nsWindowsHooks, nsIWindowsHooks )
 static const char *jpgExts[]  = { ".jpg", ".jpe", ".jpeg", ".jfif", ".pjpeg", ".pjp", 0 };
 static const char *gifExts[]  = { ".gif", 0 };
 static const char *pngExts[]  = { ".png", 0 };
-static const char *mngExts[]  = { ".mng", 0 };
 static const char *xbmExts[]  = { ".xbm", 0 };
 static const char *bmpExts[]  = { ".bmp", ".rle", ".dib", 0 };
 static const char *icoExts[]  = { ".ico", 0 };
@@ -170,7 +168,6 @@ nsWindowsHooks::nsWindowsHooks()
     jpg(   jpgExts,  "MozillaJPEG",  "JPEG Image",           "jpegfile", "jpeg-file.ico"),
     gif(   gifExts,  "MozillaGIF",   "GIF Image",            "giffile",  "gif-file.ico"),
     png(   pngExts,  "MozillaPNG",   "PNG Image",            "pngfile",  "image-file.ico"),
-    mng(   mngExts,  "MozillaMNG",   "MNG Image",            "",         "image-file.ico"),
     xbm(   xbmExts,  "MozillaXBM",   "XBM Image",            "xbmfile",  "image-file.ico"),
     bmp(   bmpExts,  "MozillaBMP",   "BMP Image",            "",         "image-file.ico"),
     ico(   icoExts,  "MozillaICO",   "Icon",                 "icofile",  "%1"),
@@ -212,7 +209,6 @@ nsWindowsHooks::GetSettings( nsWindowsHooksSettings **result ) {
     prefs->mHandleJPEG   = BoolRegistryEntry( "isHandlingJPEG"   );
     prefs->mHandleGIF    = BoolRegistryEntry( "isHandlingGIF"    );
     prefs->mHandlePNG    = BoolRegistryEntry( "isHandlingPNG"    );
-    prefs->mHandleMNG    = BoolRegistryEntry( "isHandlingMNG"    );
     prefs->mHandleXBM    = BoolRegistryEntry( "isHandlingXBM"    );
     prefs->mHandleBMP    = BoolRegistryEntry( "isHandlingBMP"    );
     prefs->mHandleICO    = BoolRegistryEntry( "isHandlingICO"    );
@@ -323,8 +319,6 @@ nsWindowsHooksSettings::GetRegistryMatches( PRBool *_retval ) {
          ||
          misMatch( mHandlePNG,    gWindowsHooks->png )
          ||
-         misMatch( mHandleMNG,    gWindowsHooks->mng )
-         ||
          misMatch( mHandleXBM,    gWindowsHooks->xbm )
          ||
          misMatch( mHandleBMP,    gWindowsHooks->bmp )
@@ -379,7 +373,6 @@ nsWindowsHooks::CheckSettings( nsIDOMWindowInternal *aParent,
             settings->mHandleJPEG   = PR_FALSE;
             settings->mHandleGIF    = PR_FALSE;
             settings->mHandlePNG    = PR_FALSE;
-            settings->mHandleMNG    = PR_FALSE;
             settings->mHandleXBM    = PR_FALSE;
             settings->mHandleBMP    = PR_FALSE;
             settings->mHandleICO    = PR_FALSE;
@@ -568,7 +561,6 @@ nsWindowsHooks::SetSettings(nsIWindowsHooksSettings *prefs) {
     putPRBoolIntoRegistry( "isHandlingJPEG",   prefs, &nsIWindowsHooksSettings::GetIsHandlingJPEG );
     putPRBoolIntoRegistry( "isHandlingGIF",    prefs, &nsIWindowsHooksSettings::GetIsHandlingGIF );
     putPRBoolIntoRegistry( "isHandlingPNG",    prefs, &nsIWindowsHooksSettings::GetIsHandlingPNG );
-    putPRBoolIntoRegistry( "isHandlingMNG",    prefs, &nsIWindowsHooksSettings::GetIsHandlingMNG );
     putPRBoolIntoRegistry( "isHandlingXBM",    prefs, &nsIWindowsHooksSettings::GetIsHandlingXBM );
     putPRBoolIntoRegistry( "isHandlingBMP",    prefs, &nsIWindowsHooksSettings::GetIsHandlingBMP );
     putPRBoolIntoRegistry( "isHandlingICO",    prefs, &nsIWindowsHooksSettings::GetIsHandlingICO );
@@ -616,11 +608,6 @@ nsWindowsHooks::SetRegistry() {
     } else {
         (void) png.reset();
     }
-    if ( prefs->mHandleMNG ) {
-        (void) mng.set();
-    } else {
-        (void) mng.reset();
-    }
     if ( prefs->mHandleXBM ) {
         (void) xbm.set();
     } else {
diff --git a/xpfe/components/winhooks/nsWindowsHooks.h b/xpfe/components/winhooks/nsWindowsHooks.h
index e820ae1ab996..22afb2c742de 100644
--- a/xpfe/components/winhooks/nsWindowsHooks.h
+++ b/xpfe/components/winhooks/nsWindowsHooks.h
@@ -92,7 +92,6 @@ class nsWindowsHooksSettings : public nsIWindowsHooksSettings {
         PRBool mHandleJPEG;
         PRBool mHandleGIF;
         PRBool mHandlePNG;
-        PRBool mHandleMNG;
         PRBool mHandleXBM;
         PRBool mHandleBMP;
         PRBool mHandleICO;
@@ -134,7 +133,7 @@ class nsWindowsHooks : public nsIWindowsHooks {
 
     // Objects that describe the Windows registry entries that we need to tweak.
     ProtocolRegistryEntry http, https, ftp, chrome, gopher;
-    FileTypeRegistryEntry jpg, gif, png, mng, xbm, bmp, ico, xml, xhtml, xul;
+    FileTypeRegistryEntry jpg, gif, png, xbm, bmp, ico, xml, xhtml, xul;
     EditableFileTypeRegistryEntry mozillaMarkup;
 
     // Give nsWindowsHooksSettings full access.