I use Radeon Pro
2x VisionTek HD3860 Cards
Use alternate frame rendering, Vsync forced off, AI advanced and force process affinity
Then use a logging program like Everest to check GPU temp/usage will tell you right away if both cards are getting work or not.
Latest 10.12 seems to favor my primary card more, so I'm back to using a modded 10.5 from Guru3D (GenetiX)
FYI using a custom profiler like Radeon Pro, I never install the crappy reg edits that ATI releases.
I have had issues with Radeon Pro not showing the GPU usages with the f8 key recently. That's why I log to check things out. In-game AA is usually better than forcing it through CCC or Radeon Pro imho.
PS (sort of relevant) a hard drive can easily be the bottle-neck in new systems as well, if your GPU isn't topped and framerate seems iffy, look at a SSD for your OS and game, use a mechanical drive for storage. Load times dropped by 75% in my case.
Edited, Jan 3rd 2011 12:07am by SpelunkerOne