last week i purchasd a sapphire radeon hd 4870 x2 2gb gddr5. i had to buy a bigger case and bought a 750w power supply to install it because of its size and power connectors.I am running windows 7 ultimate 64bit with a core 2 duo 2.5ghz,8gb ram on a asus p5g41c-m lx motherboard. i was running a palit geforce gt 240 before with no problems but now iv got the new card in it crashes every time i try start up any game. ive updated my bios,installed the latest graphics drivers and software and rienstalled them.ive updated windows,my chipset drivers,audio drivers the works. please can someone help ?