The MMC snap-ins for managing Windows Terminal Services won't allow you to see open sessions on a remote terminal server if you aren't an administrator. And even if you grant the user the permissions described in http://technet.microsoft.com/en-us/library/cc732332.aspx, the user still won't be able to run the snap-ins. How can a standard user view open terminal server sessions?
They can do this by using the Qwinsta command-line utility, which can be run by both admins and standard users. And on newer Remote Desktop Session Host (RDSH) servers they can use the Query Session command.
Mitch Tulloch is a eight-time recipient of the Microsoft Most Valuable Professional (MVP) award and widely recognized expert on Windows administration, deployment and virtualization. For more tips by Mitch you can follow him on Twitter or friend him on Facebook.