allans post is great, but, There are 2 known issues when you remove Windows Messenger. The first is when you load Outlook Express and use the Contacts pane. This causes OE to try to load Messenger, it can't and this causes a long delay. The Registry entry that corrects this is:
HKEY_LOCAL_MACHINE/Software/Microsoft/Outlook Express/Hide Messenger
A DWORD value of 2 prevents OE from trying to load it.
The second is that Hotmail's web site will load extremely slowly if Messenger is removed. Its the same type of hang that OE experiences.
The fix is to rename
HKEY_CLASSES_ROOT/Messenger.MsgrObject
To
HKEY_CLASSES_ROOT/Messenger.MsgrObjectOld
This removes the reference to the object that Hotmail tries to load, it fails, but it doesn't hang.
I don't use either of these instances, and I did not do these registry hacks after I uninstalled messenger with the method allan posts