Hello, I was working fine with Windows Messenger 4.7 and SER. I upgrade to SP2 and I cannot sign it. Not sure however SP2 modifies the remote call procedure used by windows messenger 4.7.2009 which had some security flaws. That is why 4.7.3 is installed automatically with SP2. It is not a question of removing WM5 you must revert back to the old RCP. Microsoft seems suggesting moving using windows messenger 5 for SIP, however I have found messenger 5 quite unreliable when used with SIP. Is there a way to get SIP on 4.7.2009 working with XP SP2 ? When I used Windows Messenger 5 with SER I experienced these problems: 1) users which are on-line are not seen on-line by the messenger client ( presence problem ) 2) you send a message to on-line user and you get message cannot be delivered. 3) You send a message and message does not get delivered, you do not receive an error message. Thank you, Regards, Wilhelm