If you know for sure that the time is always at midnight, then you can use equality like:
column_name = CONVERT(datetime, '2008-09-07', 105)
If time portion can vary, use ranges like:
... column_name >= CONVERT(datetime, '2008-09-07', 105)
AND column_name < CONVERT(datetime, '2008-09-08', 105)
Hope this helps, Mika