The best way to do it is like this:
Start System in safe mode
Un-install all VGA related software, including Catalyst, driver and other software like Afterburner or other tuning software.
It is important to do this on safe mode so that the registry can be cleaned.
If the system does not allow you to do remove In safe mode, please use a program like DDU , which you can dowload for instnace here: http://www.wagnardmobile.com/DDU/?q=node/38
Reboot system (normal mode).
Windows will ask to install driver, just click that away (close). For download and installation of new driver got to: http://support.amd.com/en-us/download/desktop?os=Windows%2010%20-%2064