MSN messenger starts up all by itself when you boot XP, and restarts when you fire up Outlook Express.

Here is how to stop this nonsense.

1) Run the Group Policy Editor (gpedit.msc)

2) Expand Administrative templates then Windows components

3) Option "do not allows windows messenger to be run" and "do not automatically start windows messenger initially" are the ones you want

These options can be set under both Computer Configuration and under User Configuration.