I dont know of anything to stop it other than removing the hotmail account or by disabling 'check for messages' on that account when you start Outlook. The reason it does that is because it has to authorize on that account by going to a website.
Go to Start --> Run and type regedit
Navigate to the Registry Key below.
Right click on the Messenger.MsgrObject key and select rename.
Rename it to Messenger.MsgrObjectold