I had the exact problem trying to get win7 on Asus maximus VII hero to recognize my Asus pce-ac68 wireless adapter card.
I found out, (after much frustration and cursing of the gods)
that in the bios there is a setting called "Onboard Devices Configuration"
which can be configured to one of two modes, x1 or x4.
at x1 the pciex4_3 slot (my main bitch) runs normal and all other pci slots function normal
however, at 4x (which is the default setting i was using) the main pci slot runs at high performance (good for graphics card) but all other pci slots are disabled, and although you might be able to see something connected to somewhere you'll never get it to work.
0. Bookmark this page
1. Uninstall the drivers for the ac68
2. Restart and press F2 to go into bios
3. Advance > Onboard Devices Configuration > switch to x1 > save and exit
4. Install drivers back
5. Use the bookmark to come back and let us know what happened.
hope this helped.