overclocking phenom x6 help

Hi
I recently bought a new comp with the respective specs.
processor-phenom x6 1090t
motherboard-m4a89gtd pro
ram-transend drr3 4 gb ram
smp-cooler master 550w
graphic card-4870 hd sapphire

I tryed overclocking grafic cards using overdrive which is an utility in ati catalyst software.now memory clock is 1000mhz(previously 900mhz).Please comment on this is it safe and suggest me for futher actions.
My motherboards has this function called turbo key 2,its a switch in the motherboard when i enable it and reboot the comp . I get a boot faliure with a blue screen.Ther is also an utility igiven by asus called turbo evo i tried auto tuning, my comp restarted and i got a blue screen in the next boot up and a message came overclockinbg failed ,so i reseted the bios settings , please help me i am eager to solve this prob.
TY in advance.
CHEERS FROM INDIA!

 

My graphic card after overclocking its is running at 87.c,please suggest.should i return it to default settings or not.I have an air conditioner for the room is it enough or should i mod the case.My case is iBALL BULLET.I am seriously worried about the lifespan of the card.Please comment.