I have had this happen. I cannot install new drivers over old drivers on win 10. I must uninstall first. I usually use DDU to uninstall the AMD drivers. The last time I upgrade (15.12) I uninstalled the amd drivers using the amd install manager.
When you are at the point where you install the drivers, make sure you have disconnected from the internet and have disabled ALL anti/virus/anti malware/blockers of any kind. Once the installation begins, go get a cup of coffee and just leave it alone. Most times it restarts.