Yes, as the title says, a VMware ESX can be virtualized 4.0 inside another VMware VM, and also, be able to create and boot virtual machines within our virtual VMware ESX!!! Logically we are talking about a test environment and never for production, as it is ideal for setting up your own lab if you don't have enough VMware ESX-compatible hardware 4.0 and want to try out the new features (Fault Tolerance or FT, vNetwork Distributed Switch or DVS, Host Profiles Linked VC… Let's go vSphere) or if you want to perform a testing lab… it is also done in a few very simple and quick steps.