Yes from wjhat I can see there is some confusion between MSN Messenger and Windows Messenger. Both initially look the same but the former is a user selected service (chat; e-mail etc etc) and the latter is a component part of Windows networking service.
If you do not network then I think it is OK to disable it but you run the risk of losing functionality, especially in Windows XP Pro. (I have a couple of PC’s networked together so for my particular configuration it is necessary). My instinct is to leave it well alone.