calculate TotalHours Between two dates in sql server 2005

DATEDIFF[^] will do the job for you.

SELECT DATEDIFF(hour, '2012-12-31 12:00:00.00', '2013-02-10 13:00:00.0000000');

will return 985, which is correct.

So supposing a fictive table structure since you have not specified any, this statement will summarize what the total hours:

select sum(DATEDIFF(hour, DateFiled1, DateField2)) from TableName

[Update based on new requirement]
To have a hh:mm format, you need to declare a function, or simply use following approach in your query:

DECLARE @d1 DATETIME
DECLARE @d2 DATETIME
SET @d1 = '2013-01-01 00:00'
SET @d2 = '2013-01-02 10:25'
SELECT DATEDIFF(minute, @d1, @d2)
SELECT CAST((DATEDIFF(minute, @d1, @d2) / 60) AS VARCHAR(8)) + ':' +
       right('0' + CAST((DATEDIFF(minute, @d1, @d2) % 60) AS VARCHAR(2)),2)

Of course, the last statement is the key, the rest is for demonstration.