This document discusses virtualizing private cloud resources to maximize utilization. It begins by introducing cloud computing and its service models of Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS). It then explains how virtualizing an existing private cloud using virtualization software like VMware can enable multiple virtual clouds to run on a single physical machine. This "cloud within a cloud" approach significantly improves CPU and memory utilization compared to a single private cloud.