Originally Posted by Dez
I doubt its the unofficial patch. I just recently did a clean install of skyrim to my pc and it runs flawlessly with unofficial patches. By no means I'm not an expert with skyrim mods, but if i had to make a wild quess, some unoptimized script in some other mod could easily cause such slowdown in performance. Or if you're running one of those npcs mods (like wars in skyrim) they are known to cause major slowdowns.