If the board is a newer board and has the option to boot from SCSI or IDE-0, IDE-1, IDE-2, IDE-3, network, optical, CD-ROM, etc, then disable all other boot options in BIOS for subsequent boot devices. This should help ensure that SCSI boots first.
Here's MS info on the boot.ini file and how to change this file accordingly. I believe it should be scsi(0), not multi(x), where x can be 0 or 1 (if there are two IDE controllers on board).
http://support.microsoft.com/default.aspx?scid=kb;en-us;Q314081
Here's the inverse of what you want to do.
http://support.microsoft.com/default.aspx?scid=kb;en-us;Q133491
On some motherboards there is an option to set a Type F DMA buffer control, enable this function if it is available in BIOS. If the board has options to select drives by letter to boot from [C,D,E,F] in addition to SCSI [like C,SCSI,A or SCSI,C,A] set the option to the F drive.