You cannot change your user information on the "My Settings" page in SharePoint Server 2007

When you click Edit Item on the My Settings page to change your display name or e-mail address in Microsoft Office SharePoint Server 2007, the option to change your user information is unavailable.

In SharePoint Server 2007, the user information fields are read-only fields. This behavior occurs because the user information data is pushed from the SharePoint Server 2007 profile store.

If a user manually changes this information, the information is overwritten the next time that the user information data is pushed from the SharePoint Server 2007 profile store.