I'd recommend slax; it has a pretty small footprint and is a small download(192MB):
http://www.slax.org/
It boots to a command line login; you enter "root" for user and the password is "toor". At the prompt, you run:
# startx
and you should be in kde and can run k3b. For a toram boot, do either of the below:
boot: slax copy2ram
boot: slax toram
Slax is one of my favorite livecds; it's helped me out of many jams.