Query of SQL Server

Question

Hi,

 

When i'm using the following query the result is displaying when i'm passing @StartDate='1/1/2011' and @EndDate='1/5/2011'

 

But its not displaying when i'm passing @StartDate='12/25/2010' or any date of previous year

select * from PS_MSI_LETTER_BATCH BATCH
where( convert(varchar(10),CREATED_DATETIME,101) >=convert(varchar(10),@StartDate,101) and convert(varchar(10),CREATED_DATETIME,101) <=convert(varchar(10),@EndDate,101))
But when i'm using the following query Its displaying in both the cases.i.e if i pass the previous year date or this year date.
select * from PS_MSI_LETTER_BATCH
WHERE CREATED_DATETIME BETWEEN '2009-12-31 03:31:25.760' AND '2011-01-05 03:31:25.760'
Could any one help on this???
Thanks,
Prasant