alter user problem

<p>Hi all<p>I have install Postgresql 7.3 with user name EDU.<br />then I enter the psql to change the password for EDU
using"alter user EDU with password 'aaaa''<br />it returns " user EDU do not exist".<br />I check the system table
pg_user,and the user 'EDU' actually exists.<br />But if I take the following SQL, it works<br />"create user TEST'<br
/>"Alteruser TEST with password 'dddd';<br />I check the pg_user again, and find the user "TEST' is replace by
'test'.<br/>So I have a question:<br />How I change the password for the initial user "EDU", or is it  a bug for
postgresql7.3?<br />Great thanks for any message<br />Josh.