fixing bug 2201 - changing Cancel button behaviour. r=sgehani. affects only windows platforms.

xpinstall/wizard/windows/setup/dialogs.c

@@ -1732,14 +1732,11 @@ LRESULT CALLBACK DlgProcAdvancedSettings(HWND hDlg, UINT msg, WPARAM wParam, LON
           break;
 
         case IDWIZBACK:
+        case IDCANCEL:
           DestroyWindow(hDlg);
           PostMessage(hWndMain, WM_COMMAND, IDWIZBACK, 0);
           break;
 
-        case IDCANCEL:
-          AskCancelDlg(hDlg);
-          break;
-
         default:
           break;
       }