diff --git a/mozilla/browser/components/nsBrowserContentHandler.js b/mozilla/browser/components/nsBrowserContentHandler.js
index 985d1e26c08..2dbb3d375f1 100644
--- a/mozilla/browser/components/nsBrowserContentHandler.js
+++ b/mozilla/browser/components/nsBrowserContentHandler.js
@@ -84,8 +84,7 @@ function needHomepageOverride(prefb) {
   return true;
 }
 
-function openWindow(parent, url, target, features, args)
-{
+function openWindow(parent, url, target, features, args) {
   var wwatch = Components.classes["@mozilla.org/embedcomp/window-watcher;1"]
                          .getService(nsIWindowWatcher);
 
@@ -98,6 +97,18 @@ function openWindow(parent, url, target, features, args)
   return wwatch.openWindow(parent, url, target, features, argstring);
 }
 
+function openPreferences() {
+  var features = "chrome,titlebar,toolbar,centerscreen,dialog=no";
+  var url = "chrome://browser/content/preferences/preferences.xul";
+
+  var win = getMostRecentWindow("Browser:Preferences");
+  if (win) {
+    win.focus();
+  } else {
+    openWindow(null, url, "_blank", features);
+  }
+}
+
 function getMostRecentWindow(aType) {
   var wm = Components.classes["@mozilla.org/appshell/window-mediator;1"]
                      .getService(nsIWindowMediator);
@@ -117,6 +128,7 @@ var nsBrowserContentHandler = {
     var prefb = Components.classes["@mozilla.org/preferences-service;1"]
                           .getService(nsIPrefBranch);
     this.mChromeURL = prefb.getCharPref("browser.chromeURL");
+
     return this.mChromeURL;
   },
 
@@ -215,8 +227,19 @@ var nsBrowserContentHandler = {
 
     var chromeParam = cmdLine.handleFlagWithParam("chrome", false);
     if (chromeParam) {
-      openWindow(null, chromeParam, "_blank",
-                 "chrome,dialog=no,all" + this.getFeatures(cmdLine), null);
+
+      // Handle the old preference dialog URL separately (bug 285416)
+      if (chromeParam == "chrome://browser/content/pref/pref.xul") {
+        openPreferences();
+      } else {
+        var features = "chrome,dialog=no,all" + this.getFeatures(cmdLine);
+        openWindow(null, chromeParam, "_blank", features, null);
+      }
+
+      cmdLine.preventDefault = true;
+    }
+    if (cmdLine.handleFlag("preferences", false)) {
+      openPreferences();
       cmdLine.preventDefault = true;
     }
   },
diff --git a/mozilla/browser/components/shell/src/nsWindowsShellService.cpp b/mozilla/browser/components/shell/src/nsWindowsShellService.cpp
index a17942864d7..3638a71481d 100644
--- a/mozilla/browser/components/shell/src/nsWindowsShellService.cpp
+++ b/mozilla/browser/components/shell/src/nsWindowsShellService.cpp
@@ -160,7 +160,7 @@ OpenKeyForWriting(const char* aKeyName, HKEY* aKey, PRBool aForAllUsers, PRBool
 //     firefox.exe\DefaultIcon             (default)   REG_SZ  <appname>,0
 //     firefox.exe\shell\open\command      (default)   REG_SZ  <appname>
 //     firefox.exe\shell\properties        (default)   REG_SZ  Firefox &Options
-//     firefox.exe\shell\properties\command(default)   REG_SZ  <appname> -chrome "chrome://browser/content/pref.xul"
+//     firefox.exe\shell\properties\command(default)   REG_SZ  <appname> -preferences
 //
 // - Uninstall Information
 //   ---------------------
@@ -247,7 +247,7 @@ static SETTING gSettings[] = {
     PATH_SUBSTITUTION | EXE_SUBSTITUTION | NON_ESSENTIAL },
   { MAKE_KEY_NAME1(SMI, "%APPEXE%\\shell\\properties\\command"),
     "", 
-    "%APPPATH% -chrome \"chrome://browser/content/pref/pref.xul\"",   
+    "%APPPATH% -preferences",   
     PATH_SUBSTITUTION | EXE_SUBSTITUTION | NON_ESSENTIAL }
 
   // The value of the menu must be set by hand, since it contains a localized