Windows Server 2012 – Trying with VMware Server 5.0

Changes to environment variables should take effect immediately, if you make the change via the main Properties dialog for the computer in question (go to My Computer | Properties | Advanced | Environment Variables). After the changes are saved, Explorer broadcasts a WM_SETTINGCHANGE message to all windows to inform them of the change. Any programs spawned via Explorer after this should get the updated environment, although already-running programs will not, unless they handle the setting change message.

I'm not able to tell from your problem description what specific problem you're having with this. Can you tell us more about the specific scenario that isn't working?

This KB article may also be of use: How to propagate environment variables to the system

VMWare will NOT let you change the VENDORID part of your generated MAC address. Well you can edit the VMX file but either the server won't boot or the NIC won't work - it's been about a year since i tried so i cant remember the failure behavior.

What you will need to do is spoof the mac address in windows I haven't done this in windows only *nix but a quick google led me to this link that seems pretty accurate (and since it claims to work in XP should be the same as 2k3) although a bit dated.