this may not be a real bug,but need improve
when 2 messenger accounts login on 1computer and user select the same dir to save chatlogs,the first account's chatlog will overwrite with no prompt when the second account start chat.
there's no warning texts on chatlog dir select window,and no check if that dir has some old chatlogs
()
sys : winxp sp2 Chinese simplified
messenger:7.5.0311 Chinese simplified
plus:3.62.146 Chinese simplified
