When reinstalling the FH game make sure you remove all of it's content from C:\FeralHeart before you install it again. Otherwise something might lay around still causing the game to have problems running properly.
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If you did that there might be chances of your installers that you have acting up, however though, if you reinstall the game you do not really need to download the patch, the game setup on the downloads page install the whole FH game, the patch is just for those who already have the game installed, when re-installing completely it's suggested that you use the game setup instead, and a new downloaded one as well and not the old one you had.
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If you did just that, it could be something simple like the rendering mode or graphics option used inside the game, try running different rendering modes, disabling water reflections, lower view distance etc, anything to make the game less demanding.
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And since the latest patches of FH in some cases users need to update DirectX or the C++ library on their computers. Running windows update should solve this for some.
Just a few things you could look up, make sure it's done properly though.
