Vista - Logging conversations with Windows Live Messenger

Hi,

I'm just investigating whether this is theoretically possible at the moment.
I have a small network (1 server, SBS2008 and four Windows PCs). All the
users want instant messaging, for which Windows Live Messenger suits the bill
perfectly.

What I would like to do is:

- install Windows Live Messenger on all PCs
- block other messaging clients
- have the facility to automatically log all Windows Live Conversations and
save the resulting files to a central location

The first two points are, clearly, no problem. Is the logging possible and
if so, can anyone tell me how to do it?

Cheers

Karl