It's usually picked up automatically during the activation process but if not go to Windows Settings/System and on the left scroll down to About. Under Device specifications is "Device Name". That is what I find is used as Computer ID.

Hmm... sadly, that says it is not the correct Computer ID. Thanks though.

If you are trying to install and activate a Vegas program on another type of hardware and you want to activate again somewhere there ( only 2 times)with the same email, you have first to de-activate that program on another computer or deactivate it on your Magix account.