A massively distributed processing system and associated methods are disclosed that provide a processing architecture for utilizing a multitude of widely distributed devices to process distributed project workloads. To provide the processing infrastructure, a modular client agent program, which may include a system component and a separate project component, operates on the distributed devices to process workloads. For different projects, different project components may be provided to run on the base system component. In addition, a device capabilities database and an incentive database can be used by the server system to facilitate operations and encourage participation by client systems. Other databases may also be utilized to enhance system operations and functionality. And a wide variety of applications are possible, including network site testing, network site indexing, distributed data back-up, file sharing, data caching, data conversion, and scientific research, as well as many other distributed projects.