Peer to peer BitTorrent (P2P BT) systems are used for video-on-Demand (VoD) services. Scalability problem could face this system and would cause media servers not to be able to respond to the users’ requests on time. Current sliding window methods face problems like waiting for the window pieces to be totally downloaded before sliding to the next pieces and determining the window size that affects the video streaming performance. In this paper, a modification is developed for BT systems to select video files based on sliding window method. Developed system proposes using two sliding windows, High and Low, running simultaneously. Each window collects video pieces based on the user available bandwidth, video bit rate and a parameter that determines media player buffered seconds. System performance is measured and evaluated against other piece selection sliding window methods. Results show that our method outperforms the benchmarked sliding window methods