[ubuntu] help please,,new to linux i play world of warcraft

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http://ubuntuforums.org – i am new to linux but i love it and wont go back to windows,,but i am have trouble i play world of warcraft in the game i have very low fps but in windows i had 80fps i need to fix this i am useing hp g62 ATI Mobility Radeon HD 4200 Series ubuntu 10.10,,i need to upgrade my display driver but dont know how i did use the additional drivers and installed the driver it had but it is not working so well,,i have googled this but still cant figure out how to install the driver u download from the ati website if some1 can please help me,,also my computer has 4 gigs of ram and core dual 2 ghz (Hardware)