Sometimes you want to hava a NIC in a VMware VM to have a static MAC address in stead of a dynamically generated one.
This sanbarrow.com page explains what to change in the VMX configuration file.
From:
ethernet0.addressType = "generated" ethernet0.generatedAddress = "00:0c:29:40:7e:22" ethernet0.generatedAddressOffset = "0"
To:
ethernet0.addressType = "static" ethernet0.address = "00:50:56:3e:86:29"
VMware also has a few docs on this for workstation and ESX installs and a KB article for both.
–jeroen