I have Toshiba Satellite C660
Tried to install Windows7 by selecting Sata controller as AHCI I got this message
Windows cannot be installed to this disk. This computers hardware may not support booting to this disk. Ensure that the disks controller is enabled in the computers BIOs menu.
Then I changed Sata controller to Compatibility which worked but OS running pathetically slow.
How can I use AHCI sata controller mode like I was using before?