In MAC OSX, VM Fusion can run XP from a Boot Camp partition...I was wondering if I can startup the 1st Hard Disk Windows 7 machine in a ESX VM ....
To be able to do this, ESX would need to understand the file structure of the foreign disk system, in this case Windows. ESX only works with it's own file system for it's datastores. It may be possible to create a ESX VM that uses a physical partition (which is what is happening with Fusion using the Boot Camp partition.) But not only is this unsupported, it is quite dangerous if you don't know what you're doing.
Additionally, unlike Fusion, where you use the "local console" to run Fusion and interact with the VM, with ESX, the local console is not used to interact with the VM. (It's not even a GUI.) You need to use a separate Windows workstation to run the vSphere client. So even if you were to get ESX to run a VM from a physical partition, you couldn't do anything on that one machine. You'd still need a second machine.
In general, you cannot use a machine loaded with ESX as an interactive workstation (which is what you're doing with OSX + Fusion + Boot Camp parition.) You can
host workstation virtual machines, but you need to connect to those virtual machines from another computer. (e.g.: vSphere client or RDP or VNC.)
