Try this:
This problem happens under certain circumstances or configurations. To get around this particular issue you will need to rename all of the SCSI ASPI drivers on the diskette, follow the instructions below.
**If you are using a SCSI CD Rom or Hard Disk we recommend disconnecting them while using the modified Boot Disk, as they will not be detected.
-Boot up using the Win98/98SE Boot Disk. When you reach the Startup Menu where you can select whether to start the computer with or without CD Rom Support, press the “F5” Key. This will bring you to an A:> prompt.
-Type “REN ASPI2DOS.SYS ASPI2DOS.OLD” (without quotations) and then press the “Enter” key.
-Type “REN ASPI4DOS.SYS ASPI4DOS.OLD” (without quotations) and then press the “Enter” key.
-Type “REN ASPI8DOS.SYS ASPI8DOS.OLD” (without quotations) and then press the “Enter” key.
-Type “REN ASPI8U2.SYS ASPI8U2.OLD” (without quotations) and then press the “Enter” key.
-Type “REN ASPICD.SYS ASPICD.OLD” (without quotations) and then press the “Enter” key.
-Press “Ctrl-Alt-Del” to restart the computer.
Source: http://www.promise.com.tw/techdoc/scanning_pci_bus_using_Mechanism_2.htm