A remote desktop utility system is an emerging client/server networked model for enterprise desktops. In this model, a shared pool of consolidated compute and storage servers host users desktop applications and data respectively. End-users are allocated resources for a desktop session from the shared pool on-demand, and they interact with their applications over the network using remote display technologies. Understanding the detailed behavior of applications in these remote desktop utilities is crucial for more effective QoS management. However, there are challenges due to hard-to-predict workloads, complexity, and scale. In this paper, we present a detailed modeling of a remote desktop system through case study of an Office application - email. The characterization provides insights into workload and user model, the effect of remote display technology, and implications of shared infrastructure. We then apply these learnings and modeling results for improved QoS resource management decisions - achieving over 90% improvement compared to state of the art allocation mechanisms. We also present discussion on generalizing a methodology for a broader applicability of model-driven resource management.