create table #t1 (productNo tinyint, productname varchar(10),
Des varchar(50), quantity tinyint)

Insert into #t1
select 1, 'borin', '4x-mal', 2 union all
select 1, 'borin', '5x-cal', 3 union all
select 2, 'hypoid', '4-5cal', 4 union all
select 2, 'hypoid', '4-5cal', 4 
---

;with cte as (
	select row_Number() over (partition by productNo, ProductName
				order by quantity desc /* arbitrary */) AS COLUMN1,
	*
	FROM #T1)
DELETE FROM CTE WHERE COLUMN1>1

select * from #t1
drop table #t1