Expanding a comma-sep field

[Don Briggs]

I have a table that has an ID field, and a CHAR field containing a comma delimeted list of numbers. I need a SELECT statement that will expand the list of values, and cross-join them with the tables primary key. We are using MySql Ver. 4.0.18

Here is what I have
item_id | codes
1 | 100,200,300
2 | 100,300

Here is what I need
item_id | code
1 | 100
1 | 200
1 | 300
2 | 100
2 | 300

Please Help!!!!!