There's a free tool that would enable an administrator view the current active accounts within the domain by specifying a targeted machine name to query its live sessions. One would install a utility package called Systernals to include an executable called "psloggedin.exe." An example usage for such command is shown below:

Command:
psloggedon \\{file_server_name}

Usage: psloggedon [-l] [-x] [\\computername]
or psloggedon [username]
-l Show only local logons
-x Don't show logon times

Result:
PsLoggedon v1.34 - See who's logged on
Copyright (C) 2000-2010 Mark Russinovich
Sysinternals - www.sysinternals.com

Users logged on locally:
DOMAIN1\user1

Users logged on via resource shares:
PC1\user1
PC2\user2
PC3\user3
PC4\user4
PC5\user5
PC6\user6
PC7\user7
PC8\user8

Please note that we have chosen to query the {file_server_name} instead of a domain controller or workstation because file servers are most likely to have active sessions, especially if users home folders are specified to point toward the file server in active directory. In the example above, we can easily determine who has console, physical access to the server. At the same time, we can tell which user is using certain computers by names.