Lags (FPS DROP)

Hi, so first of all i downloaded WoW Mists of Pandaria and when i run the game i have an error in error said that my drivers is too old and i need to upgrade them. So i downloaded drivers for my pc, but when i'm playing WoW i have 100fps then 10fps.. Please help. Thx!

try cleaning pc and scanning with some programs , or with antivirus if u have one :P

It doesn't work. :/

Check CPU usage - if its ok ---> turn off all addons, and see if you still drop fps.