The actual username on certain versions of Windows are not able to be changed once made - only deleted. You can change the "friendly name", that the user would see every time they log in or on the start menu, but the actual username that's used will be the original name.
To further clarify:
-I buy a computer with Windows XP loaded on it. I set it up with the username "m00c0w".
-This is what appears on the start menu and as my name for the home directory, and the actual username that's logged for events on the computer
-I sell the computer to TigerBalm, and they change the name since they bought it from me. We'll say they change it to "TigerBalm" from the standard control panel.
-The username that is logged for events will still be "m00c0w", and the home directory for the user (where all the files are stored) will still be named "m00c0w", but the name on the start menu is now "TigerBalm".
Now, there is a way to change the username, but someone who didn't really care enough about it or know how to do it would only successfully change the name that appears on the Start Menu, pretty much. Even if they changed the username, however, the directory names would still remain the same as the original name and this could also very well be where the "profile name" comes from.