Migrating VM from VMware Server 1.0.x to ESXi 3.5 | cmoud.com
In response to Microsoft releasing free Hyper-V Server (actually a full Windows 2008 Server with only one role – Hyper-V) VMware followed with crippled version of their flagship product, ESX Server. The product is called VMware ESXi Server and the current version is 3.5 update 3. Unlike VMware Server it does not require operating system to be installed first as it is actually heavily modified and customized linux-based hypervisor.