You can add this VBScript as a script to a Workstation startup script and change the default IM Warning message.

Eventually I will put it in an ADM template...

Bob Christian
[URL]www.bobchristian.com[/url]

---Begin IMWarning.vbs---
'This script will change the default warning in Windows Messenger
'Written by Bob Christian and posted to the newsgroup
'Microsoft.Public.LiveComm.General because it was easier than
'finishing the .adm template. You can place this in a workstation
'startup script. PLEASE TEST THIS IN A LAB ENVIRONMENT FIRST!
'BobChristian@removethis.gmail.com

Option Explicit
On Error Resume Next
Dim WSHShell, RegKey
Set WSHShell = WScript.CreateObject("WScript.Shell")

RegKey = "HKEY_LOCAL_MACHINE\Software\Microsoft\MessengerService\Policies\IMWarning"

WSHShell.RegWrite RegKey,"Rewrite this line to something that your legal department approves...or something that your mother would approve.","REG_SZ"

WScript.Quit
---End IMWarning.vbs---