How do I stop my computer from signing in to Y! Messenger automatically?

In Messenger, click the Messenger menu and select Preferences. On the left in the dialog box, click General. On the right, uncheck the first option (Automatically start Yahoo! Messenger) and click OK.

try it in this exact order using "sign out", not exit and see if that helps the setting to stick for you :)

let it sign in as it usually does

when you're connected (friends list loaded etc) select Messenger from the top menu

select Sign Out (not Exit)

then on the login screen, uncheck the box beside "sign in automatically"

now click Sign In, its really important you do this step with the new setting in place.

once signed in, click Messenger > Sign Out

now Messenger > Exit

next time you launch yahoo messenger it should prompt for signin :)

go into prefrences and there should be a check mark that says "log into messenger on start Up" or something close then just uncheck it and you should be fine.

uncheck automatically sign in, it will resolve your problem.