I installed 13.1 drivers for an HD 42xx card today. Steps:
1.
download the latest version of AMD drivers for the device for Windows 8 32-bit or 64-bit (match OS obviously).
2. once downloaded, run it.
3. After the initial extraction, it will pop up to continue the install.
Cancel. It will fail anyway because the OS doesn't match what the drivers are for.
4. Log in to an admin account if you aren't already.
5. right-click on the start button and select Device Manager
6. expand Display Adapters
7. Find the "Microsoft Basic Display Adapter" that needs updating and double click on it.
8. Change to "driver" tab.
9. Click "Update Driver."
10. Click the button that says you'll find the driver yourself.
11. Navigate to C:\AMD which was created by the installer in step 1.
12. ???
13. Profit!