Download the AMD Catalyst 14.4 (220.127.116.11 March 27) driver. This driver works with Windows 7, 8 and 8.1.
We have a discussion thread open on this driver right here.
Unfortunately there are no relase notes available for this driver, but it is the first one to fully support the new AMD Radeon R9 295X2.
Build Info: DriverVer=03/27/2014, 14.100.0.0000 Catalyst: 14.4 CCC: 2014.0327.2227.38483 Direct3D: 9.14.10.01029 OpenGL: 18.104.22.16872 OpenCL: 10.0.1445.5 HSA: 0.8.0.0.241 Mantle: 9.1.10.0009