Future Grid Networks should be able to provide Quality of Service (QoS) guarantees to their users. In this work we examine the way Grid resources should be configured so as to provide deterministic delay guarantees to Guaranteed Service (GS) users and fairness to Best Effort (BE) users. The resources are partitioned in groups that serve GS users only, or BE users only, or both types of users with different priorities. Furthermore, the GS users are registered to the resources either statically or dynamically, while both single and multi-Cpu resources are examined. Finally the proposed resource configurations for providing QoS are implemented in theGridSim environment and a number simulations are executed. Our results indicate that the allocation of resources to both types of users, with different priorities, results in fewer deadlines missed and better resources utilization. Finally benefits can be derived from the dynamic registration of GS users to the resources