Not sure profile work the same in every O/S you mentioned, but this is what I think about XP profiles.
Changing the name of the computer, http://support.microsoft.com/kb/295017
Changing user names...involves changing user profiles. The files reflected under Documents & Settings take their cues from the user profiles created. If you delete the user profile, then (I believe) that you can delete the related Dosc & Settings folders. When a new user profile is created, a new set of Docs & Settings folders are created for that user.
I don't believe that changing the names of the users...will eliminate the old names in the Docs & Settings folders. My understanding is that the old, unwanted user profile must be deleted.
Beyond that, I can't tell you anything useful about such...never tried it.
Edited by hamluis, 24 January 2010 - 08:37 PM.