Incorrect syntax near the keyword 'OVER'

When attempting to calculate an expression, I get the error Incorrect syntax near the keyword 'OVER'.

I'm not sure what is the error on this line:

(SUM([DCT].[Quantity_Stk] * [ICP].[UnitCost] )) - ((@PurchaseCost + @Prod_CostLBS ) * @InputWeight ) OVER (PARTITION BY [ARC].[CustomerCode] )

I was able to use OVER on another expression and it worked just fine and was formatted like the one above, except it was only taking the SUM of one column.

Full Code:

SET NOCOUNT ON; 
DECLARE @PurchaseCost Decimal(19,8);
DECLARE @InputWeight Decimal(19,8);
DECLARE @Prod_CostLBS Decimal(19,8);

SET @PurchaseCost = 2.58;
SET @InputWeight = 18100;
SET @Prod_CostLBS  = .15;

SELECT 
     CAST([ARC].[CustomerCode] AS NVARCHAR(40)) + ' - ' + CAST([ARC].[Name] AS NVARCHAR(40)) AS [Supplier]
   , [PC].ProductCode
   , [PC].Description1
   , Count(IC_ProductLots.OriginalQuantity_Alt) AS [Boxes]
   , IC_ProductLots.UnitOfMeasure_Alt
   , Sum(IC_ProductLots.OriginalQuantity_Stk) AS [Weight]
   , IC_ProductLots.UnitOfMeasure_Stk
   , [ICP].UnitCost AS [Unit Cost]
   , Sum([DCT].[Quantity_Stk] *[ICP].[UnitCost]) AS [Total Sales]
   , Avg(([IC_ProductLots].[OriginalQuantity_Stk] / [IC_ProductLots].[OriginalQuantity_Alt])) AS [Avg. Box Weight]
   , Sum([IC_ProductLots].[OriginalQuantity_Stk] / @InputWeight) AS [Yield]
   , CAST (@InputWeight - SUM(Sum([IC_ProductLots].[OriginalQuantity_Stk])) OVER () AS DECIMAL(18,2)) AS [Shrink]
   , Max(CAST ((@PurchaseCost + @Prod_CostLBS) * @InputWeight AS DECIMAL (18,2))) AS [Cost]
   , SUM([DCT].[Quantity_Stk] * [ICP].[UnitCost]) - ((@PurchaseCost + @Prod_CostLBS) * @InputWeight) OVER (PARTITION BY [ARC].[CustomerCode])
 AS [Profit]
 FROM (((( IC_Products [PC] 
    INNER JOIN  DC_Transactions [DCT] 
     ON [PC].ProductKey = [DCT].ProductKey)
    INNER JOIN  AR_Customers [ARC] 
     ON [DCT].CustomerKey = [ARC].CustomerKey)
    INNER JOIN  IC_ProductLots 
     ON [DCT].LotKey = IC_ProductLots.LotKey)
    LEFT OUTER JOIN  IC_ProductCosts [ICP] 
     ON ICP.ProductKey=PC.ProductKey and ICP.ProductCostCode=5)
 WHERE 
    (IC_ProductLots.ProductionDate >= { ts '2015-06-24 00:00:00' }   AND (IC_ProductLots.ProductionDate <= { ts '2015-06-24 00:00:00' } OR IC_ProductLots.ProductionDate Is Null)) 
AND ((1=1)  AND [ARC].CustomerKey IN (124) ) 
 GROUP BY 
     CAST([ARC].[CustomerCode] AS NVARCHAR(40)) + ' - ' + CAST([ARC].[Name] AS NVARCHAR(40))
   , [PC].ProductCode
   , [PC].Description1
   , IC_ProductLots.UnitOfMeasure_Alt
   , IC_ProductLots.UnitOfMeasure_Stk
   , [ICP].UnitCost
   , IC_ProductLots.ProductionDate
   , [ARC].CustomerKey
 ORDER BY 
     CAST([ARC].[CustomerCode] AS NVARCHAR(40)) + ' - ' + CAST([ARC].[Name] AS NVARCHAR(40)) 
   , CAST (@InputWeight - SUM(Sum([IC_ProductLots].[OriginalQuantity_Stk])) OVER () AS DECIMAL(18,2)) 
   , Max(CAST ((@PurchaseCost + @Prod_CostLBS) * @InputWeight AS DECIMAL (18,2)))

I am using Microsoft SQL Server 2005.