I assumed that the remote client is integrated into the domain.

Hmm, yes you could also check for open port 445 (Windows 2000/XP), then for the existance of admin$ (Windows NT), everything else would be Windows 9x or other OS. It's not bulletproof, howver.

Alternatively, create a list of computername/OS during logon. I don't think that computernames of remote client changes very often, thus this should give a pretty good representation independent of IP addresses of the remote clients.
_________________________
There are two types of vessels, submarines and targets.