PsLoggedOn displays logged on users for remote PCs
Mark Russinovich at www.sysinternals.com has released PsLoggedOn freeware utility displays both the locally logged on users and users logged on via resources for either the local computer, or a remote one. Full source code is included. Useful to Windows NT admin.
PsLoggedOn's definition of a locally logged on user is one that has their profile loaded into the Registry, so LoggedOn determines who is logged on by scanning the keys under the HKEY_USERS key. For each key that has a name that is a user SID (security Identifier), PsLoggedOn looks up the corresponding user name and displays it. To determine who is logged onto a computer via resource shares, LoggedOn uses the NetSessionEnum API. Note that PsLoggedOn will show you as logged on via resource share to remote computers that you query because a logon is required for LoggedOn to access the Registry of a remote system.