Tuikkal: Anyone having problems with the Ultimate SiN patch may want to try "Sin Patcher" from PCGamingWiki.
BananaJane: Thank you this patch worked but I'm getting very bad framerates =s
It might have something to do with graphical setting. I don't recall how I fixed mine exactly but try customizing your own settings, except keep the resolution you prefer (Typing the desired value by opening the Sin Patcher and keeping it 1152x864 in game's own options). Putting anti-aliasing and anisotropic filtering on low in the options might help as well (You can force better ones from graphics driver panel).
You can also fix the frame rate by opening the console after the level loads then enter cl_maxfps XXX (XXX being your desired frame rate). Between 60 to 100 should do it.
All of this sounds like hassle and it is, but finally finding a way to fix it has its own reward :)