I am building a computer with a 128 GB SSD and a 1 TB HD using Win 7 64-bit. I know before I install Win 7 I want to enable AHCI in bios, what I had some questions about is does AHCI mostly pertain to the drive the OS is on? Do you enable it for each individual drive you are using? I am planning in plugging in my old 500 GB HD to move data from it to the SSD and/or 1 TB HD, there won't be any issues because it's from an old computer not using AHCI will there? Probably pretty dumb questions, but I just wanted to understand it better. [e] Also to prevent a 2nd thread, is it important to install the OS with only the SSD plugged in or can I have another HD in at the same time and just specify install to SSD?