The computing needs of enterprises are typically met by purchasing or using existing dedicated high-performance compute resources. An alternative, proposed in this presentation, is to meet these computing needs by harnessing under-utilized resources across the enterprise. This represents a form of grid computing in the enterprise that is extremely cost-effective and substantially improves the return on investment in existing computer resources. The primary source of under-utilized resources are PCs and, in the aggregate, represent a dominant source of compute power. The UD MetaProcessor software represents these resources as a single large grid service for administrators, application developers and users. In this talk, I will present some of the challenges with this grid service together with some of the solutions to these challenges. A number of case studies will show the immediate benefits of adopting this technology to satisfy computational needs today. The sheer amount of compute power available also enables feasible solutions to problems that were previously discarded as being impractical or impossible to solve.