If you need IDEfix and/or want to continue using it, download IDEfix97 from Aminet, unpack it to RAM, open IDE-fix/Register and run the Register program to enter your key number.
If you want to get rid of IDEfix, open Devs/DosDrivers and drag CD0 or EMERGENCY_CD (whichever exists) over the Editpad icon in AmiDock in order to edit it. In the text change DEVICE=atapi.device into DEVICE=scsi.device. Then delete all #?atapi#?.device from Devs and IDEfix and LoadIDE from C.
If you do the latter, you cannot use the second channel of a 4-way IDE spliter any more. Both drives (HDD and CD) need to be connected to the first channel as master (Unit=0) and slave (Unit=1).