Well I would suggest you follow the instructions I will provide. You are now only using the CPU portion of your APU because your onboard graphics are disabled. I do believe there are several models of the R7770, not sure which one you have but that doesn't concern me.
Here we go 1st use the un-install instructions, 2nd use DDU (Display Driver Un-installer) and then 3rd install instructions. I would download 13.9 CCC package to install. The un-install and install are found in How to Forum written up by stumped. The DDU will remove any left over software, registery or directories that are still left out there on your system.
Display Driver Uninstaller :
AMD A10-5800K, XFX 7850 Ultra OC Edition 975MHz 1gb, 16GB RAM, Win 8.1 Pro 64 bit, MSI 7778 motherboard, 500W PSU, HP P7-1235, CCC 13.9 WHQL