— Desktop grids use the idle cycles of desktop PC’s to provide huge computational power at low cost. However, because the underlying desktop computing resources are volatile, achieving performance guarantees such as task completion rate is difficult. We investigate the use of buffering to ensure task completion rates, which is essential for soft real-time applications. In particular, we develop a model of task completion rate as a function of buffer size. We instantiate this model using parameters derived from two enterprise desktop grid data sets, evaluate the model via trace-driven simulation, and show how this model can be used to ensure application task completion rates on enterprise desktop grid systems.