If i downloaded oblivion patch version 1.2.0416 do i need to also need to download shivering isles patch version 1.2.0416 for shivering isles?
There is an Oblivion version and a SI version of the latest patch. If you don't have SI download only the Oblivion patch. Do not download the Oblivion version of the patch if you have SI. If you have SI download only the SI version of the patch.
That said, if you got them both as GOTY it should already be patched. when you load up the game it should say in the lower left corner of the screen which version of the game you have.