SIP, VoIP and Windows Messenger....

Greetings,

We've recently aquired some VoIP enabled routers to connect some of our stores. Everything works fine, I can call each router without a problem.

On the router features it is said: "...you can receive calls from users of compatible PC software, notably Windows Messenger...". This could have lots of uses on our company.

Now, I can't seem to put that to work and I can't find any info (for dummies!) on the internet, but after looking around at the Messenger's settings, I'm guessing I will need a SIP server? If thats the case, will Exchange 2000 do the job as with IM?

As a sidenote, no connection to any .NET service is allowed so a LAN solution would be required.

If someone could shed some light over this or point me to the right direction I would be very grateful!