|Does your system boot from a SCSI drive? Most don't nowadays. Most use IDE or SATA. If you're actually booting from a SCSI drive then check the SCSI bios settings, the drive's cable and the drive's ID jumpers.|
If you're not booting from a SCSI drive then there must be some problem with your IDE/SATA drive, its cable or its configuiration in cmos/bios setup.
If you have no SCSI devices at all then disable the SCSI controller in cmos/bios setup or, if it's a SCSI card, remove the card.
It'd probably be a good idea to post your system specs, including drive types or model numbers.