Look at the following and see if it helps.
DECLARE @d AS FLOAT = 72
SELECT
@d,
CAST(@d AS VARCHAR(10)) AS StingVal,
CHARINDEX('.', CAST(@d AS VARCHAR(10))) AS Position,
CASE
WHEN CHARINDEX('.', CAST(@d AS VARCHAR(10))) = 0
THEN CAST(@d AS VARCHAR(10)) + '.0D'
ELSE CAST(@d AS VARCHAR(10)) + 'D'
END AS DesiredVal
The code works in 2008 but should also work in 2005