Net /send and WIN98 (Sending Messages)

We are using Windows 2000 Advanced server and a mix of Win 9X and Win 2K workstations. Previously we had Netware Server and one good feature we had was the ability to send a message to all the workstations or selected users (by login name or groups). This ability helped us in asking them to shutdown a certain applicaton or notify them of the server going down etc.

Since we shifted to Win 2K we have lost this ability. Ofcourse “Net /send” can be used but messages are only sent to Win 2K machines and are ignored by Win 9X machines.

I would appreciate if someone could point to a low overhead, preferrably free, utility which is transaparent to the user and solves the problem.

Thanks