Flustered over ICS (Internet Connection Sharing)

Alright well my network is functioning right now but I want it to work a special way. Right now I have my cable modem and router downstairs. The router has 1 connection to a computer downstairs next to it which is running vista, and it is also connected to a printer and network drive which are downstairs, the last connection runs upstairs to a computer running xpPro. The computer upstairs has a motherboard with dual rj-45 connections. What i wanted to do is use the 2nd ethernet jack with a crossover cable to connect to another computer also running xp to share internet and possibly files and drives. Using these two guides Link1 and Link2 i have came up with an understanding of what needs to be done, but i just cannot seem to get it working properly. :cry

Alright the main problem. When i go to enable ICS (internet connection sharing) on the host computer for the connection that is functioning, i keep getting the error,

"An error occurred while Internet Connection Sharing was being enabled.

Internet Connection Sharing cannot be enabled.
A LAN connection is already configured with the IP address that is required for automatic IP addressing."

I understand that this problem is due to the address 192.168.0.1 needs to be open for ICS to function. So i manually set my router to have the LAN at 192.168.0.101, so now when i ping 192.168.0.1 it comes back timed out. Yet it still does not work!

I am terribly confused now and have no idea where to go from here, thank you in advance to anyone who read this through or attempts to help me in any way!

 

Rather than doing the ICS upstairs, reset your router to the original working state, get a switch, plug the cable from the downstairs router into it and use separate cables from the 2 upstairs comps into it.
The downstairs router is assigning IP addresses and when you enable ICS on the comp upstairs, you get conflicts because it wants to assign IP addresses.

 

Yes I was aware of this solution, but are you saying that the proposed is not possible, the conflict the router and pc are having asigning IP's is not possible to fix? I am sure i could set my router to not set them with a static DHCP or something, but you are probably right, I will just get a cheap switch, thanks for the response!

So... whats the best, and cheapest switch with at least 3-4 outputs? that maintains my full connection with zero bottlenecking?