Even though BitTorrent-like file sharing is successful for P2P (peer-to-peer) content-sharing over Internet, it suffers from the content unavailability problem when the contents are not popular (i.e., the absence of seed). This content unavailability can be mitigated by using multi-swarm cooperation and/or by bundling popular/unpopular contents. In this paper, by employing user-driven virtualized nodes, we propose a content availability improvement method in a BitTorrent-like file-sharing system. The virtualized node is assigned to (and driven by) the user node so that it can help the user node to accelerate the P2P download by taking advantage of the swarm it belongs to. We evaluate the performance of proposed method by simulating a practical BitTorrent file sharing scenario and by comparing the download completion time.