How to use a SQL CASE statement to count rows with a 0 value

SELECT     sum(CASE when S.Compl between 1 and 20 AND S.risk = 1 then S.risk else 0 end) AS AMTGain, -- it's good perfect
           sum(CASE when S.Compl between 1 and 20 AND S.risk = 0 then S.risk else 0 end) AS AMTLoser,
        
FROM       tbl_Transact AS S with (nolock)
           join tbl_Custs as u with (nolock) on s.idutente = u.idutente 
 
WHERE (u.testuser = 0)  -- no test user
AND (CONVERT(CHAR(8), S.Date, 112) BETWEEN '20080520' AND '20080520')