Here is what I did, you can choose to do as you wish.
1. I created a Welcome User Group
2. I created a user "CP Greeter" and assisgned this user ID to that group as it's primary user group.
3. I created a sub-forum called "welcome" and allowed html code.
4. I edited the Amy's VERY nice xml code to reflect the user ID of CP Greeter and the forum ID.
This way, when a user registers, the forum post is automagically created under my CP Greeter profile and he welcomes our new users!
See it in action here:
http://www.cpfools.com/forum/forumdisplay.php?f=91