How much RAM does it have? I found one review online (dated 2001) stating that
the C600 comes with 128MB. That's not enough for Ubuntu. But yours might have
more.

Having said that: I run Ubuntu 11.04 on a Toshiba laptop that's almost as old.
It's a Pentium III (three!), clocked at 1.1GHz, with 512MB of RAM.
Responsiveness at the desktop level is satisfactory, and a bit better than the
Windows XP installation it had when I got it.

The Wi-Fi PCMCIA 802.11b card "just worked", without any tinkering on my part.
Interestingly, it supports WPA encryption under Ubuntu. (The Windows driver
would only support WEP.)

If you've got enough RAM on the C600, try Ubuntu. Otherwise, you might want to
try Puppy Linux.