IF OBJECT_ID('tempdb..#Parts', 'U') IS NOT NULL DROP TABLE #Parts
CREATE TABLE #Parts
(
  ID int,
  ID2 int,
  PartNo varchar(10)
)
SET NOCOUNT ON
INSERT INTO #Parts (ID, ID2, PartNo) Values (75, 23921, 'DENT')
INSERT INTO #Parts (ID, ID2, PartNo) Values (75, 26145, 'PLGD')
INSERT INTO #Parts (ID, ID2, PartNo) Values (75, 26145, 'PRRP')
INSERT INTO #Parts (ID, ID2, PartNo) Values (75, 26145, 'SIST')
INSERT INTO #Parts (ID, ID2, PartNo) Values (75, 57290, 'PRMD')
INSERT INTO #Parts (ID, ID2, PartNo) Values (75, 57290, 'abc')
INSERT INTO #Parts (ID, ID2, PartNo) Values (75, 57290, 'def')
INSERT INTO #Parts (ID, ID2, PartNo) Values (75, 57290, 'ghi')
INSERT INTO #Parts (ID, ID2, PartNo) Values (75, 57290, 'jkl')
SET NOCOUNT OFF
 
SELECT ID, ID2,
Max((Case When RowNumber = 1 Then PartNo Else '' End)) AS Part1,
Max((Case When RowNumber = 2 Then PartNo Else '' End)) AS Part2,
Max((Case When RowNumber = 3 Then PartNo Else '' End)) AS Part3,
Max((Case When RowNumber = 4 Then PartNo Else '' End)) AS Part4
FROM
(
  SELECT ID, ID2, PartNo,
  ROW_NUMBER() OVER(PARTITION BY ID, ID2 ORDER BY PartNo ASC) AS RowNumber
  FROM #Parts
) AS tbl
GROUP BY ID, ID2

ID          ID2         Part1      Part2      Part3      Part4
----------- ----------- ---------- ---------- ---------- ----------
75          23921       DENT                             
75          26145       PLGD       PRRP       SIST       
75          57290       abc        def        ghi        jkl
 
(3 row(s) affected)

ID          ID2         DENT       PLGD       PRRP       SIST
----------- ----------- ---------- ---------- ---------- ----------
75          23921       1          0          0          1
75          26145       1          0          1          0
75          57290       0          1          0          1