SELECT GETDATE(), CAST(GETDATE() AS VARCHAR(25)), CONVERT(VARCHAR(25), GETDATE(), 21)

Hmm... something to think about when you need to get precision conversion.
Never assumed that CAST will produce the expected result. 2006-08-12 01:31PM is a lot different than 2006-08-12 13:31:43.390 (43.390 seconds lot).