A. In some ways they are stricter than NT 4.0 when you consider that you used to be able to upgrade from NT Workstation to NT Server (but not to a PDC or BDC) but this is not possible in Windows 2000. Windows 2000 gives better upgrade paths from the Windows 9x operating systems.

The upgrade paths you can perform are:

Windows NT Workstation -> Windows 2000 Professional
Windows NT Server -> Windows 2000 Server, Advanced Server, Datacenter
Windows 2000 Advanced Server -> Windows 2000 Datacenter

You cannot perform the following upgrades:

Windows NT Workstation -> Windows 2000 Server, Advanced Server, Datacenter
Windows 2000 Professional -> Windows 2000 Server, Advanced Server, Datacenter
Windows 2000 Server -> Windows 2000 Advanced Server, Windows 2000 Datacenter