A Virtual Observatory (VO) seeks to provide access to very large volumes of astronomical data over the internet to every interested user, along with software for the data anlysis, and tools for data visualisation, statistics and any other applications which are necessary for mining science from the data. Handling large volumes of data requires extensive computer resources, which may not be available to the end user; transferring data from the data centre to the user needs high bandwidth, which also may not be available. A VO therefore seeks to provide computing resources as well, which could be spread over a grid. The user can locate data of interest through registries, then access the data and analyse it using the computing resources, all through simple user interfaces.