What would be the easiest way to set up a second server to act as an archive system?

I have NE now and would want to set up a secondary FOSS server on a subdomain. I would take old NE accounts from employees who leave and send them over to the FOSS box.

Something like: NE on domain.com > FOSS on archive.domain.com

I'd probably use a VM for the FOSS box rather than devote a whole server to it. Hell, I might even just set that up on the main NE box as it will have 8gb of RAM and could spare a gig or so.