Powercolor HD6870 drivers won't install correctly

Hey r/techsupport, I'm stumped by this one. I put my HD6870 in, put the driver CD in, installed the drivers - the installer installs some things (an SDK, HydraVision etc) but doesn't install the Catalyst Control Center, then just exits to the desktop without actually installing the drivers. I tried uninstalling the drivers, wiping all traces off using Driver Sweeper and CCleaner (rebooting in between) and reinstalling, but every time it does the same thing. I also tried the official drivers from the AMD website, same problem. I had this issue before (I have a new mobo and HDD, so fresh install) and the problem was that I wasn't plugging in both 6 pin PCI-E power connectors to the card, so the mobo wasn't seeing it. However, I've got both cables plugged in this time (coming from my Antec HCG 750W, so under capacity power is not the issue) and I've tried both PCI-E lanes on my Gigabyte GA-Z68AP-D3 but the same thing happens every time. Someone please help!

Thanks guys!