Do you play other games?
At first I'd try reinstalling driver to the graphic card.
To do it,
1. download the newest driver from
here and some program to clean after the old driver (can be Driver Cleaner),
2. deinstall the present driver you have on your PC (in control panel-> deinstal programs), restart pc,
(2a.) probably do some finish for the deinstallation (afair there comes up another window of deinstaller after restart) and restart again,
3. run driver cleaner - clean your pc, restart,
4. install the new driver, restart,
5. check if it worked.
I'm pretty sure not every single restart is needed, but it's always safer - so that you wouldn't later need to repeat the whole procedure from the beginning because maybe something was (de-)installed uncompletely.