Internet data center providers are still struggling to lower the operational costs of their data centers. One reason is the low utilization of servers over a long period of time during the day. We describe a system for optimizing the server resources within Internet data centers, which host different services such as Web servers or enterprise resource planning systems. The system, called resource management system, allows Internet data center providers to allocate their resources in an economically efficient way. The results may indicate that there is free capacity or a lack of capacity. Based on the results, the resource management system can sell or purchase resources on the Grid. The idea behind this approach is to enable Internet data center providers to gradually transition from the current environment to an environment where utility computing is possible. Our approach separates between the local resource allocation and the external one (Grid).