There isn't any point in doing that. CS:S is Steam only, so if you want to play, you have to update.
They have released like 3 patches in the past few days, it is a much more robust system than having all these different executables and different versions floating around.
They could release HL2 in 10 days and release 4 patches before it even hits the stores using the preload/update system in Steam.
(my guess is end of Sept).