Acer AcerAltos 19000 User Manual page 159

Be sure that both standard hard disks are mapped out of the computer using
the Setup program by setting the Setup program to No Drives Installed.
Be sure that the SCSI boot drive is set to SCSI ID 0 and that there are no SCSI
ID conflicts. Check the drive installation manual for information about setting
the SCSI ID for that device. You can use the SCSISelect utility to determine the
SCSI IDs of devices on the SCSI bus.
Be sure that parity checking is consistently enabled or disabled on all devices
on the SCSI bus. See the section "SCSI Parity Checking".
Try enabling Include in BIOS Scan in the SCSI Device Configuration option of
the SCSISelect utility. See the section "SCSI Device Configuration".
Be sure to cycle the power OFF and ON after changing any values on a SCSI
controller, in a Setup program, or on a SCSI device. Doing this ensures that
the new initial values are loaded.
Be sure that the SCSI bus is properly terminated. See the section "Setting SCSI
Bus Termination".
Be sure that the intended boot disk has an active partition and has been
formatted.
Check cable connections and pin-1 orientation.