NT 4 domain Upgrade to Win2 mixed mode

I have a very old nt 4 pdc and my remote site BDC’s in different subnets but connected via vpn are fairly new and running nt 4 also. Here is my question. I cannot upgrade my PDC since it is a very old system and the hardware will not survive the upgrade. I have a new box that I would like to just install 2000 server so it takes over as pdc in mixed mode. I know that the only way to migrate the users and groups is to upgrade the PDC to windows 2000 and run in mixed mode. I could install NT4, promote to PDC and upgrade to windows 2000 but that will probably be not too clean and I am trying to avoid that. Any insight or suggestions on this would be appreciated.