diff --git a/layout/xul/base/src/nsMenuPopupFrame.cpp b/layout/xul/base/src/nsMenuPopupFrame.cpp
index b750ae15db9..c389502b7b7 100644
--- a/layout/xul/base/src/nsMenuPopupFrame.cpp
+++ b/layout/xul/base/src/nsMenuPopupFrame.cpp
@@ -861,18 +861,13 @@ nsMenuPopupFrame::SyncViewWithFrame(nsPresContext* aPresContext,
     screen->GetAvailWidth(&screenWidth);
     screen->GetAvailHeight(&screenHeight);
   }
+
+  // keep 3px margin to the right and bottom of the screen for WinXP dropshadow
+  screenWidth -= 3;
+  screenHeight -= 3;
   screenRight = screenLeft + screenWidth;
   screenBottom = screenTop + screenHeight;
   
-   // inset the screen by 5px so that menus don't butt up against the side
-  const PRInt32 kTrimMargin = 5;
-  screenLeft += kTrimMargin;
-  screenTop += kTrimMargin;
-  screenRight -= kTrimMargin;
-  screenBottom -= kTrimMargin;
-  screenWidth -= 2 * kTrimMargin;
-  screenHeight -= 2 * kTrimMargin;
-
   PRInt32 screenTopTwips    = NSIntPixelsToTwips(screenTop, p2t);
   PRInt32 screenLeftTwips   = NSIntPixelsToTwips(screenLeft, p2t);
   PRInt32 screenWidthTwips  = NSIntPixelsToTwips(screenWidth, p2t);