Helping people with computers... one answer at a time.
You're not alone, I see this a lot. If you're not careful, it's very easy to accidentally give someone else access to your account if you use MSN Messenger a public computer or someone else's computer.
It require's a little diligence on your part, or you're going to get into trouble.
First, if it's already happened, change your password now. That will prevent any "Remember Me" functionality on other computer from working any longer, because of course they'll have remembered the old, now wrong, password.
Now, each time you use someone else's computer for MSN Messenger, you need to make sure the features are off.
To keep Messenger from automatically starting at login, and from allowing automatic login. Click on Tools, Options, General. Now UNcheck "Automatically run messenger when I log on to Windows", and "Allow automatic sign in when connected to the Internet".
We also need to force Messenger to forget who we are.
The next step that everyone seems to overlook is simple: Sign Out -> Hit the File Menu, and select Sign Out.
Now at this point you'll see that Messenger may still remembers who you are, AND remembers your password. So UNcheck: Remember Me, Remember my Password and Sign me in automatically.
At this point you should also click on "Forget me".
If you ever use Messenger on someone else's computer, you must check these settings each time you are done, or you risk leaving your information on their computer.
I've put together a short, less than two minute video walking through the steps to disable the automatic login and remember me features of MSN Messenger that you'll need to take each time you finish using it on someone else's computer.
Watch the video: Preventing MSN Messenger from Starting and Signing in Automatically.