Since Roadrunner has apparently started limiting the number of dynamic IPs 
it'll let one cable modem get, I need to figure  out a way to share the 
connection.

I've got three machines on my home network, all of which are connected
via a hub, which is also connected to the Roadrunner modem. FWIW, I'm
running Mandrake 8.1 on two of the systems, including my main work
system, and Windows 2000 on the third.  My main system has no trouble
in picking up an IP address from Roadrunner when booting; my
daughter's machine is unable to.  

Right now, I've got my daughter's machine as 192.168.0.2 on my local
net, and am running my machine with two IP addresses: the one I get
from DHCP (65.25.234.54 at the moment), and a virtual IP of
192.168.0.1 -- is there some reasonable way I can use this as a
gateway for 192.168.0.2, and how do I do it?

The Masquerading How-To provides very clear instructions, which just
don't seem to work.

Any ideas?