Download the AMD Catalyst 14.x BETA (14.300.1005.0 August 27) driver. This driver works with Windows 7 and 8.1.

We have a discussion thread open on this driver right here.

This driver originally supported only the new Radeon R9 285 video card, now it has been modified to support desktop and mobile cards (you can check the supported card list in the forum post).
So treat this driver as an unofficial one since it has been modified.

The original driver can be found here.

Build Info:
CCC: 2014.0827.2250.39168
D3D: 9.14.10.01061
OGL: 6.14.10.13083
OCL: 10.0.1573.4
Mantle: 9.1.10.0034
Mante API: 94209
HDAudio: 9.0.0.9905