In windows 98, when that message came about it was generally caused by cable failure or drive failure. Remove the drive and see if you can slave it to another computer and run diagnostics from the manufacturer's utillity to check the drive....Try to swap the cables from the drive to the motherboard and see if the drive shows up in the POST screen or in the BIOS.....

If by chance that you have a SATA harddrive then the BIOS may have changed and you need to reset the BIOS drive setting to SATA....or you will need to install the motherboard sata driver by the F-6 method when you do the restore!