Which Op System as host?

shouldnt matter too much but i would make sure youre running the 64bit version to ensure that you can run a 64bit VM as well (also if youre running VMs youre going to want plenty of ram so youd be hindered by 32bit 4gb max anyway)

Cheers..

I might try an experiment with Windows 2008 to see how it performs in terms of memory. At the moment, I only have 12GB memory installed in the Windows 2011 SBS server and memory is maxed out when running a couple of VM's. CPU is sitting waiting for something to happen   I really don't need or utilise the full potential of Windows 2011 SBS so it would be an intersting experiment.

Declan

If you are used to working in the Windows Server environment then your best bet would probably be running Windows Server 2008 R2 Standard or Windows Server 2012 Standard with the Hyper-V role for your host OS. You can then run VMs of Windows XP/7 and other Windows Server VMs.

The other option of course would be to install ESXi HyperVisor on the physical machine to run your virtual machines on. This would require you having a second computer to work with, though, as you cannot set up and manage your system on the same physical machine that your ESXi is installed upon. You need another computer in the network to install the vCenter software.

You can run Vcenter in a VM. Many people do this.
http://kb.vmware.com/selfservice/microsites/search.do?c...

Your host OS should be a server OS, not a workstation OS like Windows 7 or XP. Just my opinion. And personally, if you're running a Microsoft Windows server OS, you should run it on top of Hyper-V. They tend to integrate well, but I've only worked with Hyper-V as opposed to other hypervisors, so I can't speak to them.

Indeed that's how we run vCenter or you can even run the vCenter Appliance, however you still need another machine to connect the vSphere Client to vCenter.