That was my first impression as well, but it appears there are a couple of 12.2 driver :
- a 12.2 *preview* driver (the one you linked) which does not support HD 79xx
- a "before-certification" driver (12.2 final) which adds HD 79xx support
http://support.amd.com/us/kbarticles...ieddriver.aspx
Anyways, I don't know enough about the Windows installer to comment intelligently on what the issue might be, but I do know that the earlier drivers for HD 79xx did include OpenGL support and did seem to run OpenCL apps pretty well (at least to the extent I didn't see comments in the reviews).