We're currently running virtual servers inside VMWare absolutely fine. I'm sure a Mac Pro will be able to virtualise a copy of Windows 2000 with no problems at all.
That thread says pretty much the same thing. It's probably not going to work, and even if it does, it's probably not a great idea.
Actually, the thread raises a great point. Why not just boot XP? XP and 2000 are very close, except XP has a better driver architecture that would work better with the Mac Pro, and is officially supported.