In windows XP we can easily rename our Administrator Account.
Follow the steps below to change your administrator name.
1. Type gpedit.msc from Start Menu -> Run then Press ENTER key from keyboard then you see a window(Group Policy).
2. In the Group Policy window go to Computer configuration -> Windows Setting -> Security Setting -> Local Policies -> Security Option then select from right side box Accounts:Rename administrator account by double click administrator then type name as your wish then press OK.
3. Restart the Computer
4. Your Administrator name changes to new name what you had type.