I am booting form a CD. My HD has crashed.
Have a Toshiba Satelite 1805-S274.
First I did not put the stick in USB and started Knoppix Kernal 2.4.26. It shows in the fstab file 4 entries(sda1, sda2,sda3,sda4):

#Added by Knoppix
/dev/sda1 /mnt/sda1 auto noauto, users, exec 0, 0

This is after plugging in the Stick in the USB port. It shows Hard Disk Partition [sda1 thru sda4] on the desktop. But if I click on anyone it gives error Could not mount.Not a valid block device.

So subsequently

I logged in as root and did
#mkdir /mnt/flash
then when I type in
#mount /dev/sda1 /mnt/flash
It gives error
#Mount: /dev/sda1 is not a valid block device

I have tried mounting /dev/sda2, /dev/sda3 and even /dev/sda5. Nothing works.

If I tried to edit fstab file, and remove those entries.
It doesn't allow me to save it.

Second Try:

I have tried first putting the stick in USB and then booting.
Knoppix.
It syas in the beginning USB found, managed by Hotplug. Rescanning .. [001 002]

After the desktop comes up, It shows 4 partitions on the desktop
Hard Disk 1 thru 4 but no sign of Stick. If I clik on any of them it says

Step 1:
Could not mount device
Mount: /dev/sda1 is not a valid Block drive

Step 2:
Have run Utilities, Tools, USB Viewer. After a long time it shows i the left panel:
USB OHCI Root Hub
... usb-storage
If I click on usb-storage it shows all the details of the
device including the correct size etc.
Which means it has recognised the USB stick

But it doesn't show it in the the 'fstab'

Step 3:

Now how do I mount it? What to do with these non-existing hard drives?

By the way I am a Professor of IT and have used in the past
SCO Xenix. But that was 10 years ago.

Thanks a million for your patience and help.