Scsi present but not enabled/configured at pci bus location 00:11

Scsi present but not enabled/configured at pci bus location 00:11

This is the message when I try to boot a pc with an Asus P3b-f and an Adaptec 2904CD with w98 boot disk. I try to change controller, mobo and pci slot with no results. I tried also to assign irq 11 to the controller (default is "auto").
So I used a hd with w98 pre-installed, and in w98 the controller works perfectly (Pioneer Dvd works very well).
What could be the problem in dos?