how can i fix colorful lines issue on my fedora background ?

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there are colorful lines on my screen when i use fedora 20 or 18 . even when i just open terminal then the screen becomes dark and i cant identify any thing("i can do functions but i cant see them properly") . its something like graphic issue but i dont have such a problem in windows 8. i have x64 machine(HP pavilion g6 amdA4-x64) and i tried fedora 20-x64 kde (dual win8/fedora) also i have cpu heat problem during fedora graphic :radeon graphic amd