Most desktop applications execute on commodity operating systems and networks that support end-user requirements on a best-effort basis. As a result, the end-user cannot indicate to the underlying system the priority of networked applications when they are executed concurrently. Consequently, the performance of these applications is degraded non-deterministically based on the availability of resources and furthermore the degradation is not in the order and to the extent the end-user would want. This unpredictable degradation frequently affects the usefulness of a user session when multiple networked multimedia applications are executed simultaneously. We designed and implemented a prioritization service that allows an end-user to prioritize applications according to the requirements of an individual session. We report on our experiences during the implementation and our solutions to the difficulties encountered. Our performance analysis demonstrates effective prioritization when multiple applications are executed.