networing problems
 

hi all, i am trying to share my linux pc's internet connection with another computer running win xp pro, they are connected using a crossover cable.
i have a dual boot pc, running linux mandrake 10, an win xp pro.

however i have this strange problem, my internet connection is through usb, and i have 2 ethernet ports aswell. now when i boot in xp everything works fine, (sharing ineternet connection, shared folders etc)

but when i boot in linux, i am unable to share my internet with the other xp computer, need help with this.

also when i boot into
linux and dont have n e ethernet cables plugged in, linux starts up fine, and my internet works, my internet connection (through usb) is broutht up as : - eth0 - VIATECHNOLOGIES - USB
and my two network cards as : - eth1 - REALTEK RTL8139
and :- eth2 - REALTEK RTL8139.

but when i boot with a ethernet cable plugged into 1 of my network cards, it start up fine, but wont detect my usb connection and just brings up
: - eth0 -REALTEK RTL8139
and : - eth1 - REALTEK RTL8139 .

wot can i do to solve these problems, take in mind i am very new to using linux, and need detailed help. but know that wont b a problem, cos have already had some excellent help off ppl from this site before. thanx for reading. and post bak asap, and let me know if u need more details.

1 more thing, i use my other ethernet card for other things, and want it free, so please dont suggest, hooking my modem up to my computer using an ethernet cable insted of usb. :-)