You could try some methods to find the App and call TerminateProcess()....bit nasty...
Better...remover the startup from the registry under
Code:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
Personally, I like the app telling me when I have some hotmail, so I kind of like it around....If you like this too, you can appear invisible by default by using a script I wrote....
It works in Windows Scripting Host, and grabs an interface to Messenger......then it makes you appear offline...
I put it in my startup folder on My pc at work..... so on logon, it waits for MSM to connect and logon, then changes the status....
Not very good if you are on dialup, but if you connect to the web on logon, its quite effective...
The script is dowloaded from and discribed here