Over 90C idle on video card

I have the fan on the 8 months old video card running at 100% (think hair dryer ) and at idle, i'm at ~90C, if i put the fan on 20%, it goes over 100C. When i start a game at low setting Counter Strike: Source, I can play for maybe 20 minutes and then the screen turns off while the computer still runs, So i'm guessing the video card kinda died. It's been like this since I got the graphic card, but my ex-girlfriend bought it for me and i can't return it anymore (girlfriend turned into ex-girlfriend) Help me please!

Graphic Chipset: ATI Radeon HD 5700 Series (it's the 5770)
PCIE, 1GB GDDR5
Core Clock in MHz 850MHz
Memory Clock in MHz 1200MHz
Total Memory Bandwidth in GByte/s 76.8
Software, Driver Packaging Version :8.911-111025a-128242C-ATI
Catalyst Version 11.11
Last updated on December 5th 2011

I have the Intel Core 2 6600 @ 2.4GHz, 4GB of ram
I'm running 32bit Window 7 OS

is there anyway you can remove the heatsink from the card and clean it and the chip and repaste it ?
i think thats the only way your going to get the temps down on it. the only other thing is to buy a new card.
btw it's not overclocked is it?
scrooge