honestly it sounds like part of the old driver is stuck in the system still , put the old gpu in and look in control panel in add / remove a program for amd ccc , select it .
if you run an intel cpu just select express uninstall ,
if you run an amd cpu select custom , in the next box select the drivers and ccc only .
after that is done use ddu " display driver uninstaller" in safe mode to remove all traces of the drivers and clean the registry . select clean and shut down .
then install new gpu , boot pc and install the drivers