Using a restricted IM client for internal communications

[Gantlett]

Hello,

We have a client in a very small environment consisting of two sites, with two computers in each site.

The client needs an IM solution, but the solution must support user restrictions. We must be able to restrict users from logging in using their personal IM accoutns and/or adding their friends.

Does anyone know of such a solution? I've googled around but couldn't find anything.

Thanks in advance!