Trying out Windows Server 2008. Tested it in VMWare 5.x (!) on Windows 2000 (OK, so I am still using Windows 2000 on my main machine). Hardware is AMD 4200+ with 2G RAM. And here are some tips on "converting" a Windows Server 2008 to a workstation.
BTW, if you are/were a high school or university student,go to DreamSpark to download Windows Server and Visual Studio etc for free.