Connect the two computers directly - "Network Adapter" to "Network Adapter" - using a *CROSSOVER* ethernet cable.
Enable "Internet Connection Sharing" on the actual internet connection (modem connection) in the PC that is online ("Host PC") and the "Client" PC will have internet access provided the Host is running and connected to the internet.
Have a look at this posting, which is primarily intended for doing what you want via an "Ad Hoc" wireless network rather than by cable. However the comment about IP addressing is still relevant. click here
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