We propose a novel low-cost video-on-demand architecture for heterogeneous peer-to-peer networks. The key idea of this architecture is to aggregate peers' storage and bandwidths to facilitate on-demand video streaming. To achieve this goal, we split published videos into segments and distribute them to different peers. When watching a video, a peer searches the corresponding segments, and then aggregates bandwidths from multiple supplying peers to stream the video. Instead of relying on the powerful servers/proxies, this architecture exploits the oftenunderutilized peers' resources, which makes it costeffective. We demonstrate the effectiveness of this proposed architecture through extensive simulation experiments on large, Internet-like topologies.