I purchased a sapphire radeon rx 280 3 gb as an upgrade for my Nvidia 550ti gb. But after installing the card and the amd driver, I start to get random freezes from time to time, and the window will have a problem booting afterward. There are often times when it goes to repair mode with no result, and i will take multiple manual restart for it to start up.I tried using driver unstaller to clean Uninstall the graphic drivers for both amd and nvidia, I also tried ccleaner to clear the registry but the same problem remains. I formatted the boot drive and reinstalled the window.I now unplugged the card from the motherboard and using integrated graphic driver and the window still freezes. I am running out of options here and I really need someone to help me out on this. (The computer was running fine before the video card and driver installation.)