An F6 disk refers to a diskette containing device drivers that are required to install XP, but are not included on the XP install CD. During install there is a message at the bottom of the screen to "Press F6 to install drivers" or some such. This is when you would put in the diskette to load your SATA drivers because the XP install CD does not contain SATA drivers. I guess I just assumed that you had done this or your hard drive should not have shown up at all. My bad for assuming.
You know, this might be key to the whole LBA business. By disabling LBA mode in the BIOS, that allowed XP to see the drive but it still wouldn't know that it is SATA and couldn't communicate with it properly. Hence the "disk read" error.
The Windows 7 installer does have SATA drivers, so there are no problems with it. AHCI is Advanced Host Controller Interface which is part of the SATA spec and the type usually assigned to SATA device drivers.