What exactly is a ESX Whitebox you ask? It’s a VMware ESX server running on hardware that is not exactly in VMware’s Hardware Compatibility List (HCL). Most home IT pro’s will probably be familiar with VMware Workstation, VMware Server or even other products like Xen or Sun’s VirtualBox. While those other products are relatively easy to install, none really match the power (in my opinion) of what you get with VMware ESX.
Take a look at my ESX Whitebox Article for details on how you can build your own and a comparision of when and where to use VMware ESX and some of the other products on the market.