Sounds like he is using MS Proxy Server.

>>>>You can pay more and get static IP addresses (I have a dynamic one, but it hasn't changed yet. Maybe if I turn the modem off.) I have two PC at home networked (so one PC has two ethernet cards) and I am using software so both can access the net. This works well too.
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>Thanks for the detailed explanation, but maybe I didn't make my question clear. (You sort of answered it anyway...)
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>I was confused about how one machine could be hooked to the internet through the cable modem, and the other machine, hooked to the first, could use the same internet connection. With a dial-up connection using a regular phone line, I don't think it would be possible, because the first wired machine would need to "forward" the IP packets to the second. But the fact that it is the modem that has the initially connected IP explains a little. I guess it is acting as a router of sorts.
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>BTW, connecting to the drive of a remote machine through TCP/IP is pretty cool. At one client's site, I have a development machine set up to automatically map a drive to a remote web server share through the internet. I can treat the drive as a local network drive:copy files, open them, whatever. I can even open a table inside VFP and browse it... from 1200 miles away.