V&M

 

I'm guessing here that you've set Incredimail to start up whenever Windows starts up, if this is right, you could go into Incredimails Tools/ Options, and untick "Automatically log on to MSN Messenger" (not sure if this even exists, but Incredimail is extremely close to Outlook Express in it's design)

 

If this doesn't help, it could be another program that starts up when Windows starts up (Hotmail? Outlook Express? probably an email program)