I have Knoppix 4.0.2 with Kernel 2.6.12 from CD on my PC and try to access a 2.5" USB Harddisk in an IDE-USB adapter case. So far I am not able to identify a suitable device in /dev. cat /proc/partitions just shows my two SCSI harddisks and their partitions, nothing more.

Googling provided some clues:
In order for the USB disk to be recognized as a mountable block device, the modules usbcore, usb_ohci (or usb_uhci) and usb_storage must be loaded. No problem with usbcore and usb_storage, both are loaded OK.
usb_uhci and usb_ohci cannot be loaded, however.
Both modprobe usb-ohci and modprobe usb-uhci fail with the message FATAL: modul usb_* not found.

To confuse me further, still, I found some forum posts stating that the 2.6.x-kernels are not supposed to have/need those two modules anymore.

So, here is my questions:
What am I supposed to do in order to have my usb disk recognized as a mountable block device?
Where do I get and how do I integrate the missing modules?

Thanks, Ralf