There is an add-on program for messenger, called Messenger Plus.
Warning!! When you download the program, pay attention to what you allow. DO NOT ALLOW the sponsors programs or you will be allowing a bunch of stuff you reeeeealy don't want into your computer.
MsgrPlus will put an event log into your documents and settings, along with chatlogs. I don't remember (if I ever even knew) if you can set it for "Any user of this computer" or if it is login specific.http://www.msgplus.net/
Read through all the info before downloading and use at your own risk.