Deleting multiple rows based on the first instance of the value
If this was SQL Server 2012 or later version, you could use the FIRST_VALUE window function:

WITH cte AS
  (
    SELECT
      FirstColC = FIRST_VALUE(ColC) OVER (PARTITION BY ColA ORDER BY ColB ASC)
    FROM
      dbo.Table1
  )
DELETE FROM
  cte
WHERE
  FirstColC % 2 = 0
;


In SQL Server 2005 FIRST_VALUE can be replaced with a correlated TOP (1) + ORDER BY subquery:

WITH cte AS
  (
    SELECT
      FirstColC = (
        SELECT TOP (1)
          ColC
        FROM
          dbo.Table1 AS toprow
        WHERE
          toprow.ColA = main.ColA
        ORDER BY
          ColB ASC
      )
    FROM
      dbo.Table1 AS main
  )
DELETE FROM
  cte
WHERE
  FirstColC % 2 = 0
;