If you are talking about open networking...then yes you should be able to set up a home based network the same as with any router. The difference is that you might have to actually contact the ISP and have their techs configure it for you. I have seen some that required their tech support and I have seen some that didn't. The basis is that the router itself may not be accessable by the end-user.

Sharing is not based on networking but controlled by profiles in each computer on the network...So make sure that your computers have sharing capabilities.
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I have seen some ADSL that do not use a router but a joint user profile which is set up strictly by the ISP(phone company) in which the second computer must also be connected through the telephone lines as a wired connection. Is this what you have? If so then I am sure that networking and sharing files are not allowed in this context. Only the sharing of the internet connection!