This can only be done while logged on to an administrator
account. It cannot be done from within a standard account.
If you change the password
for the user account you have set to have Windows 7
automatically log on to, then you will also need to change it here as well.
Setting your computer to automatically log on to a user account at startup could pose a security risk if you share the computer or there are other people about that could use your computer. If your computer logs on automatically, they will have the same access as whatever user account you have set to be logged on to at start up.