>Thanks Mike. Is Win2k Server the only option?

Yup.

>If Server is what is required, does the "Upgrade" option for Win2k Server apply to anything other than NT Server? (in other words, Win9x, WinME, WinNT WkSt, Win2k Pro)

I'm not sure if I know what you mean. You can upgrade any Windows OS to Windows 2000 Server.