What I tried was this:
SELECT i.pdID, i.custID, IsNull(c.CommID, 0) AS CommID
FROM tableOLD i
INNER JOIN tableCust c ON c.ID = i.CustID
LEFT JOIN tableCOMM c ON c.ID = i.CommID
This brings back all the rows I need - all 200000 of them.
And, if in the OLD table, if i.CommID is null, it returns 0.
That is what I needed.
Now, this new problem is, which I am not seeing yet is it's breaking the FK constraint in the new table.
CommID returns values from 0 - 7.
tableCOMM has PK's from 1 - 7......(was about to type 0 - 7)
Arrrrgggggg, I see it now..... DOH!!