The paper presents an implementation of QoS library redirection (QLR) for DiffServ in Microsoft Windows systems. In the QLR method, the legacy application obtains packet pre-marking ability without any modification of source codes. We have upgraded the FTP and vic (video conferencing) applications by using QLR in our Microsoft Windows testing platform. Our experimental results show that this approach can use really effectively and provide high performance of the QLR in Microsoft Windows systems