Is it possible? How can I do it?

go to hard drive and clear your hardrive cache. im into PC gaming now so I dont remember that well but that should be correct.
clearing your cache just deletes your updates nothing else.

Damn thing, I can't play that save without the update it tells me. So I am forced to start a new game if I don't want the patch?! BS! I can see. It letting you play without patches on an online game but this is a single person RPG! What's the harm if I don't want the damn patch?

Thats what happened to me on Oblivion when i played console It would not load the saved game.

What's wrong with 1.3?

Deleting the cache will revert you to the 1.0 version which will not work with the release day 1.1 patch save files.

If your save file is based on a newer patch things could get really dicey (Unpredictable) on a lower patch so they block it by default. Imagine if they changed the quest flow to fix bugs but then you tried to load into a version that didnt have those changes after the fact everything quest related might just break or the game would crash.