Due to the content bundling and the dramatic increase of content size, the download performance in peer-to-peer networks has become a research focus again recently. In this paper, we propose a novel approach to improve the download performance based on the classical space-time trade-off. With the approach, a peer can speed up local downloads in peer-to-peer networks by contributing a portion of local hard disks for the content distribution in peer-to-peer networks. The contribution can bring performance improvement to each peer following the approach and in the meantime improve the overall content distribution performance in a peer-to-peer network. Based on the approach, we propose BISTRO, a BitTorrent based on space-time trade-off. The BISTRO is compatible with the vanilla BitTorrent. Our extensive experiments show that BISTRO can significantly reduce the download time.