most times a slow screen can mean your computer doesn't have enough memory to run well. the computer specs they list for the game are not correct. all the SH games need twice the memory and video card power that they say it needs.
one thing that will help your computer is to turn off the event camera. to do this go to game options and turn it off there. the event came is one of the things that slows the game down the most and can even cause the game to go into slow motion and sometimes even CTD because of memory limitations.
another thing you should do is look into the windows memory fix so window can use all the memory that you do have. certain versions of windows will only use 3GB max and cant use any more then that until you apply the fix for it.
these may help, see if they apply to your situation:
http://www.subsim.com/radioroom/showthread.php?t=151588
http://www.subsim.com/radioroom/show...62#post2009762