I'll try to fill in the details you left out...
You installed Windows 8.1 first, and then tried to install Windows 7, but that fails.
Windows 7 is asking for something, that did not happen with Windows 8.
There is nothing in the BIOS you need to turn off for Windows 7. Have you changed anything in the BIOS?
My guess is you have your OS drive connected to one of the two ASMedia SATA ports, and Windows 7 wants a driver for that chip before it can continue.
If you just move the SATA cable to one of the two AMD SATA ports, you should have no problem with Windows 7.
If Windows 8 is still on your OS drive, you may want to format the drive in Advanced Installation.