Okay, so ESXi is free, and is a great product but does have some limitations, one of which is the cloning of VMs. This article will show you a quick and easy way to achieve this.
You need access to your ESXi server command line, either using the VMware Remote CLI appliance (http://www.vmware.com/download/vi/drivers_tools.html and look for Remote CLI), or you can use the UNSUPPORTED way which is to give yourself SSH access to your ESXI server directly. The latter is the method I prefer.
