--- a/toolkit/components/maintenanceservice/serviceinstall.cpp
+++ b/toolkit/components/maintenanceservice/serviceinstall.cpp
@@ -159,19 +159,19 @@ UpdateServiceDescription(SC_HANDLE servi
   LOG(("The service description was updated successfully.\n"));
   return TRUE;
 }
 
 /**
  * Determines if the MozillaMaintenance service path needs to be updated
  * and fixes it if it is wrong.
  *
- * @param service            A handle to the service to fix.
- * @param currentServicePath The current (possibly wrong) path that is used.
- * @param wasFixNeeded       Out parameter set to TRUE if a fix was needed.
+ * @param service             A handle to the service to fix.
+ * @param currentServicePath  The current (possibly wrong) path that is used.
+ * @param servicePathWasWrong Out parameter set to TRUE if a fix was needed.
  * @return TRUE if the service path is now correct.
 */
 BOOL
 FixServicePath(SC_HANDLE service,
                LPCWSTR currentServicePath,
                BOOL &servicePathWasWrong)
 {
   // When we originally upgraded the MozillaMaintenance service we

--- a/toolkit/components/telemetry/TelemetryHistograms.h
+++ b/toolkit/components/telemetry/TelemetryHistograms.h
@@ -314,16 +314,17 @@ HISTOGRAM(PLACES_FRECENCY_CALC_TIME_MS, 
  * Updater telemetry.
  */
 HISTOGRAM(UPDATER_STATUS_CODES, 1, 50, 51, LINEAR, "Updater: the status of the latest update performed")
 HISTOGRAM_BOOLEAN(UPDATER_UPDATES_ENABLED, "Updater: Whether or not updates are enabled")
 HISTOGRAM_BOOLEAN(UPDATER_UPDATES_AUTOMATIC, "Updater: Whether or not updates are automatic")
 HISTOGRAM_BOOLEAN(UPDATER_SERVICE_ENABLED, "Updater: Whether or not the MozillaMaintenance service is enabled")
 HISTOGRAM(UPDATER_SERVICE_ERRORS, 1, 30, 31, LINEAR, "Updater: The number of MozillaMaintenance service errors that have occurred")
 HISTOGRAM_BOOLEAN(UPDATER_SERVICE_INSTALLED, "Updater: Whether or not the MozillaMaintenance service is installed")
+HISTOGRAM_BOOLEAN(UPDATER_SERVICE_MANUALLY_UNINSTALLED, "Updater: Whether or not someone manually uninstalled the service.")
 HISTOGRAM_BOOLEAN(UPDATER_STAGE_ENABLED, "Updater: Whether or not staging updates are enabled")
 HISTOGRAM_BOOLEAN(UPDATER_HAS_PERMISSIONS, "Updater: Whether or not the updater has permissions")
 
 /**
  * Thunderbird-specific telemetry.
  */
 // Disable this application-specific #ifdef ftb. (See bug 710562)
 // #ifdef MOZ_THUNDERBIRD

--- a/toolkit/mozapps/update/nsUpdateService.js
+++ b/toolkit/mozapps/update/nsUpdateService.js
@@ -1693,36 +1693,47 @@ UpdateService.prototype = {
       Components.utils.reportError(e);
     }
   },
 
 #ifdef XP_WIN
   /**
    * Submit a telemetry ping with a boolean value which indicates if the service
    * is installed.
+   * Also submits a telemetry ping with a boolean value which indicates if the
+   * service was at some point installed, but is now uninstalled.
    */
   _sendServiceInstalledTelemetryPing: function AUS__svcInstallTelemetryPing() {
     let installed = 0;
+    let attempted = 0;
     try {
       let wrk = Components.classes["@mozilla.org/windows-registry-key;1"]
                 .createInstance(Components.interfaces.nsIWindowsRegKey);
       wrk.open(wrk.ROOT_KEY_LOCAL_MACHINE,
                "SOFTWARE\\Mozilla\\MaintenanceService",
                wrk.ACCESS_READ | wrk.WOW64_64);
+      attempted = wrk.readIntValue("Attempted");
       installed = wrk.readIntValue("Installed");
       wrk.close();
     } catch(e) {
     }
     try {
       let h = Services.telemetry.getHistogramById("UPDATER_SERVICE_INSTALLED");
       h.add(installed);
     } catch(e) {
       // Don't allow any exception to be propagated.
       Components.utils.reportError(e);
     }
+    try {
+      let h = Services.telemetry.getHistogramById("UPDATER_SERVICE_MANUALLY_UNINSTALLED");
+      h.add(!installed && attempted ? 1 : 0);
+    } catch(e) {
+      // Don't allow any exception to be propagated.
+      Components.utils.reportError(e);
+    }
   },
 #endif
 
   /**
    * Submit a telemetry ping with the int value of a pref for a histogram
    *
    * @param  pref
    *         The preference to report