there are some ways this can be done but it would force the user to do something like maybe create an account and tie their account down to that pc by reading some details off it, but if something happened like their cpu/motherboard/hdd died, this would change the IDs that would be read and would obviously stop it working but you couldn't allow them to change it when they want as they could just spoof it and change it when they get banned, plus if this was implemented it would have to have details stored on a webserver of some sort and obviously would stop working if the server went offline