1
Admin password is stored as MD5 of the password so you need to run query like
update `xoops_users` set pass=MD5('admin_pass_goes_here') were uname = 'admin';
update `xoops_users` set pass=MD5('admin_pass_goes_here') were uname = 'admin';
update `xoops_users` set pass=MD5('admin_pass_goes_here') were uname = 'admin';