I'm not sure what this post is about, but I'm going to assume that a USB Key is a memory card that fits into a USB port. I already have a USB memory card on my pc with my knoppix configuration settings on it . I copied the contents of the 3.7 live cd into a folder on my Windows (Fat32) 2000 hard drive using the Knoppix TOHD /dev/hda1 cheatcode. I then set up a 4.3GB secondary IDE drive and use 2 partitions on that for my persistent home directory (/dev/hdc1) and my swap file(dev/hdc2) . The USB drive shows up on my desktop as /dev/sda1.
I put the Knoppix cd into the cd drive, at the boot prompt type "knoppix fromhd=/dev/hda1 home=/dev/hdc1 myconf=/dev/sda1" and as soon as the kernel boots, I take the CD out of the cd rom drive and I'm up and running. If I want to boot into Win 2000, I just take the knoppix cd out and boot from hd.
To give the USB drive read/write privlidges, all I did was right click on the device icon, click on the permissions tab, and uncheck the RO box. Since I boot from the cd, I have no sign on security the way I would if I used the install to HD options, but I've never really been stuck . I downloaded Firefox 1.0 onto my /dev/hdc1 , installed it to my desktop, and use it all the time. I can't wait to get knoppix 3.8 so that it will be part of the core system.
If I change my desktop settings, or my Firefox bookmarks, I select Knoppix/Configure/Save Knoppix Settings, save everthing I can, and at the locations prompt, I check the box for Sda1 and I'm done.
I can even take the cd and the usb card to a friend's windows PC, throw in the Knoppix cd, boot as Knoppix myconf=/dev/sda1, and get the same desktop I have at home (assuming of course the target PC sees my usb card as sda1).