Unique values in a combo box

[macattack]

I'm fairly new to Access and I've been at this for quite a while now and can't figure out how to make only unique values show in my combo box. In the picture I show lots of "1"s. If I move "ID" to the right of Serial # and select unique values, it removes duplicates entirely (meaning there are now NO 1s, while I still need there to be one 1).

I'd prefer to avoid making all new tables because that's just going to complicate things further; I already have 28 tables. I am running access '10.

Row Source:
SELECT DISTINCT ATU.ID, ATU.[Serial #] FROM ATU ORDER BY ATU.[Serial #];
shows all duplicate Serial #s

SELECT DISTINCT ATU.[Serial #], ATU.ID FROM ATU ORDER BY ATU.[Serial #];
Removes anything that has a duplicate (now there are no 1s)

Mac

 

[macattack]

Ok, I'm rather confused by the fix I just luckily guessed. The solution was to have two Serial # fields and to turn unique on.