http://www.mysql.com/doc/en/Upgrading-from-3.23.html

---------------------------------------------------------------
3.23.x				4.0.x
---------------------------------------------------------------
query_buffer_size		removed
myisam_max_extra_sort_file_size(befor 4.0.3, MB)
		myisam_max_extra_sort_file_sizeafter 4.0.3, Bytes)
myisam_max_sort_file_size(befor 4.0.3, MB)
		myisam_max_sort_file_size(after 4.0.3, Bytes)
myisam_bulk_insert_tree_size	bulk_insert_buffer_size
query_cache_startup_type	query_cache_type
record_buffer		read_buffer_size
record_rnd_buffer		read_rnd_buffer_size
sort_buffer		sort_buffer_size
warnings			log-warnings
---------------------------------------------------------------
SQL_BIG_TABLES		BIG_TABLES
SQL_LOW_PRIORITY_UPDATES	LOW_PRIORITY_UPDATES
SQL_MAX_JOIN_SIZE		MAX_JOIN_SIZE
SQL_QUERY_CACHE_TYPE	QUERY_CACHE_TYPE
---------------------------------------------------------------
safe_mysqld		mysqd_safe
---------------------------------------------------------------

to 4.0.x

[command run]	mysql_fix_privilege_tables
[OPTIONS]	 ISAM -> MYISAM mysql_convert_table_format database
		or 'ALTER TABLE table_name TYPE=MyISAM'

EOF