I am sure that the below message is pretty familiar to you if you are working on P2V migrations. Basically, when you try to configure PROD/Mail ip back to the VM after P2V, you will come across this message.
"The IP address XXX.XXX.XXX.XXX you have entered for this network adapter is already assigned to another adapter"
Message says that the earlier NIC with this IP is still there in the VM, but not visible as it is not attached to the Hardware/OS currently. Windows shows the above message to remind you that there was a NIC earlier with the same IP. I have seen this message after VMware hardware upgrade also..
It is always better to do clean up post a P2V, instead of just skipping this message. Below mentioned the simple, two line step, which you can run on a VM after P2V to clean up these old NIC card devices and associated drives as we no longer need them.
1) Go to Start > Run
2) Type "cmd" and Enter
3) execute below mentioned commands
4) Run both the commands in the same command prompt, because the first command actually forces device manager to start with the ability to see non-present devices when second command is executed.
5) Once Device Manager is open, click View > Show Hidden Devices.
6) Expand the Network Adapters and here you will see the old NICs which is displayed as grayed out.
7) You can remove them one by one. You can also click the check box to remove old drivers, if there is an option.
8) Now you can configure the new NIC with the IP.