What Mikel_4 said. But for an easier way to remove your drives and re-installing your drives, you can download "DDU" to cleanly remove your drives. Once you have downloaded and installed "DDU," boot into safemode (type Windows+R to open the run program and type in "msconfig," select "Selective Startup" w/load system services and Load startup items checked, then head into the "Boot" tab, click on "Safe Mode" and restart your PC). Once your in safe mode, run the DDU program and click the first option. It will automatically remove your drives entirely, you will then be prompted to restart your PC. You'll be back onto your normal account, that's where you can either use your installation disk, or just go onto their website and download the drives. After that, you're going to have to restart your PC, you should then be set.
But Mikel's way is also easy haha.
LINKS:
DDU v.17.0.3.1 -
http://www.guru3d.com/files-details/display-driver-uninstaller-download.html
Radeon 470 Drives - http://www.gigabyte.com/products/product-page.aspx?pid=5990#dl