This paper presents a virtual hierarchical overlay network– VIRGO for scalable Grid computing. This virtual hierarchical overlay network is self-organizing and decentralized, with an effective lookup protocol for routing messages. It contains an n-tuple replicated virtual tree structured network that differs from DHT-based P2P networks and random unstructured networks cached by least-recently used (LRU) and minimum difference (MinD)replacement strategies. It retains the partial-match query and robust aspects of unstructured P2P and the advantage of effective routing and guaranteed searching of structured P2P. The time complexity, space complexity and message-cost of VIRGO is O(logN), where N is the total number of nodes in the network. Since LRU and MinD replacement strategies are used for caching route nodes, VIRGO is also a load-balanced network.