I also use a Abit AV8 with ONE ATA Hard Drive and ONE SATA hard drive.
Not sure if your config is the same but the way I got it set up is:
ATA is boot drive (c
so BIOS is set up 1) floppy, 2) CDROM,
3) HARD DRIVE
If you want to use the SATA as boot you must choose 3) SCSI
Not sure about the last phrase but that is the way it worked on my other Abit boards