To turn your situation on its head - if this is a secondary DC (i.e. doesn't hold any major FSMO roles), why not demote to a member server, install VMWare, and create a virtual DC in its place?
I thought DCs and virtuals wouldn't mix well, but I've been running a DC on hyper V for a few months now without a hitch. In addition, I've brought it up during a couple of calls I put in to MS for VM related issues, and they don't really recommend against virtualizing a DC. (obviously I wouldn't have both DCs as virtuals on the same box - definitely defeats the purpose)
To address a point raised above, your host OS should ALWAYS have a NIC separate from the one(s) used by the virtual network(s). That would avoid any possible network oddness from a shared NIC.