well, that should work, the only thing i can suggests is don't use USING
WHERE software.Manufacturer IS NULL
They should be NULL... but the resultset should only contain the rows that have NULL at the software.Manufacturer field after the JOIN.
I used exactly the smae statements to create and fill the tables, only changing the table name, and afterwards I deleted 10 rows from software...
So my resultset should have ten rows. Instead it outputs all 1000 rows filling all fields from table software with NULL.