Xfx radeon hd 4870 xxx factory overclocked game crashes

So with this VGA all my games crashes after few minutes of playing and sometimes pc restarts. And often my internet browser crashes. Can be something wrong with ATI Overdrive? What GPU Clock and Memort clock should be (mhz)? And what fan speed should it be? Now GPU clock is 775Mhz, Memory clock - 950Mhz, Fan speed - 16% and temperature ~73*C. Im sure my VGA drivers are newest and works fine.

The temp of your cars is way to high dude
it should be MAXED at ~66*C

I suggest to lower your 'GPU clock' just to lower it a bit, then play for around 15 min.
and lets say, to restart your pc after, as a result it would cooldown more
and try the same process again with 30 min
if it still go's over ~66*C then lower it more..

another suggestion is to buy a cooler..
wich isnt much for the cost and is easily done aswell..
Anyways hope this would help you out of the crashes

Update the cards bios from xfx website.