First, I would check Windows Update. Win8.1 (and Win7) must be fully updated with all 'critical' and 'optional' installed before trying to install any AMD driver. You should recieve a message "There are no more updates available" ...if not, keep installing until you get the message.
Run this program > Fix SFC /scannow errors that were not repaired
DISABLE any anti-virus/anti-malware/anti- anything while downloading and installing the drivers.
Thank you for the reply.
I had performed this sfcfix scan thing in my own time and it was indeed what fixed the problem! It performed some kind of DISM fix on the file mentioned and that allowed me to install the new drivers!
Thanks for the help