It depends on what version of VMware you have
For the most part yes
THere is also a version of VMWare that runs its own OS (Based on RH linux

) that is the host OS then you can run any OS on top of that.
The general version of VMware you can use windows or linux as the host then run any OS's on top of that.
Its great in a large environment when you have numerous servers that you want to give its OWN server to, but don't want to allocate a physical server.
In a NT4 Environment its good for BDC's because you don't want to allow users to connect to a BDC for permission reasons, but its still a spare server on the network to ask as a backup domain controller.