A. Use the net sessions command, however this will only work if you are an Administrator. You can also use control panel and choose server.

Related: Determine the Machines Users Are Logged On To

The resource kit utility, Net Watch, can also show current logged on users that are connected to the Netlogon share if you connect to the domain controller, however these connects terminate after a finite amount of time so will not necessarily show all users.

Related: List Locally Logged-on Users