You say very clearly that BOTH computers are cable connected to the router. But you also say that the wireless is set up on the second computer too. So not too sure what's going on there.

You haven't mentioned what the second computer reports when you look at the network icon.

Also what happens if the second computer (with Wirelss disabled) is connected in the router slot of the first compuuter? That'll narrow things down to the second computer (and possibly the Wireless setup), I'd warrant.

Anyway, assuming that the TCP/IP stacks in both computers are identically configured, try connecting the second computer directly to the DSL modem via ethernet. Again that should tell you something about the setup in the second computer.

Have you got Wireless turned ON in the router and is that what you're rying to connect with on the second computer?

Now I don't know how YOUR DSL modem works; if it's not configurable, then your PPOE setting in the router is prolly correct. If it is configurable (i.e. you can address it from a browser) AND if it is the DSL modem that supplied credentials to the ISP, then you would want to set the router t DHCP enables, not PPOE.

A number of things to be thinking about. SHould be solvable if you've got the first computer running; we just have to sort out what's different.