The situation is this: I have a PC with cable modem connected via a
long inverted or crossed over, I don't know how this UTP cable layout
is called, it's when both endings are different and you use them to
connect 2 PC. Anyway, this cable goes to my moms PC and she enjoys
Internet thanks to my connection.

I'm going to add a 3rd, slower computer, to use as a always on server,
so the cable modem is going there, as is the other network card in
which the modem connects.
So my question is, if I add a 3rd network card to this server PC, can I
use 2 inverted cables to connect to the other 2 clients PC?
The server is gonna be windows 98 SE, one PC is win 98 SE too and mine,
the best, is XP. I do this because I don't wanna keep mine always on,
so please, don't try to convince me to use the best as a server... ITS
A NOOO

The idea behind this is to save me from paying the HUB.
Please, don't tell me they are not THAT expensive. I rather save the
money for something else.
Any ideas about how to do this, greatly appreciated.