Here is the link to the VM tool
http://www.vmware.com/products/converter/
1. Have your ESXI box running on the network.
2. Install this on the physical server to be converted to VM:
http://www.vmware.com/products/converter/
Its free...
3. Run 'converter' on the physical server. Choose 'This local server' as the source, and then the IP address, root login & password for the ESXI box you want to send the vm to.
Depending on the size of the physical server, it will take some time.
The 'converter' program will run on the physical server and copy block by block the hard drive(s) over to the running ESXI on the network as a new VM within ESXI.
4. After the conversion is done, Power off the physical server and log into ESXI & power on the new VM.
Keep your old physical server around for a while just in case.
You will have to re-activate windows as it now detects new hardware.
Pull up the activation window and choose to activate by phone. Tell the person your talking to that you have just converted a physical machine to VM and you need to re-activate.
They will give you a new key.
Microsoft doesnt care if you remove a system from 1 machine and install on another, as long as your not over using your license.
Microsoft Windows virtualization licensing rules (summed up very briefly) are as follows:
Windows Server 2003/2008 Standard Ed. - 1 VMs licensed per physical server
Windows Server 2003/2008 Enteprise Ed. - 4 VMs licensed per physical server
Windows Server 2003/2008 Datacenter Ed. - unlimited VMs licensed per physical server (licensed per physical CPU socket on the host)
And the usual downgrade rights apply.
So if you install 2003 server on a physical machine, you can only do it 1 time. If your installing on a VM, you can use the same key 4 times if you have an Enterprise license.
(Some one might chime in here if I'm off on licensing.)