I don't think it's impossible to know when someone opens a conversation window, afaik using MSNP10 the RNG packet (which tells the user-client to connect to the switchboard) is still sent when a contact opens their window...
dmsn - by chronic student on 05-25-2006 at 06:16 AM RE: dmsn - by Re-Mi on 05-25-2006 at 07:03 AM RE: dmsn - by chronic student on 05-25-2006 at 08:26 AM RE: dmsn - by RaceProUK on 05-25-2006 at 10:17 AM RE: dmsn - by chronic student on 05-25-2006 at 10:38 AM RE: dmsn - by Re-Mi on 05-25-2006 at 10:54 AM RE: dmsn - by chronic student on 05-25-2006 at 11:26 AM RE: dmsn - by RaceProUK on 05-25-2006 at 04:52 PM RE: dmsn - by chronic student on 05-25-2006 at 07:30 PM RE: dmsn - by Voldemort on 05-25-2006 at 08:26 PM RE: dmsn - by andrewdodd13 on 05-25-2006 at 08:38 PM RE: dmsn - by RaceProUK on 05-29-2006 at 01:23 PM