How to get a Mac machine onto network

Networking setup on the Mac is actually quite painless and usually easier than setting it up on a Windows box (seeing as I have had both for quite a while that's just my opinion).

The Mac will by default use DHCP to get an IP address, the same as windows. If you need to statically set something you just go into the Mac System Preferences (which is by default under Applications) and then click on the network settings.

Here you can statically address it if such a thing is necessary.

Your comments about wi-fi not reaching from "downstairs" to "upstairs" has me puzzled. I have owned a large number of wireless devices over the years and have never had a wireless access point that could not reach up a single floor of a regular home. Is this a three story or larger building? Lots of concrete and metal?

Perhaps the wireless in her router is simply defective... if it is one that is supplied by the cable company you can always just have them swap it out.

Another option is to turn off or disable the wi-fi that is built into the device and just connect another wireless access router/bridge (with decent range) onto one of the four network switch ports.

You can simply connect the "internet" port on most routers to one of those four switch ports and for basic internet access it will work (you will be double NATTED but this does not cause a problem usually for basic email, web-surfing, etc).

You could also get a router that can run either TOMATO or DDWRT open source firmware and google for guides on how to set the device to run in "bridging" mode. In this mode the wireless network acts as a transparent link between wireless devices and the wired network. In other words the computer will get an IP via DHCP, etc, from the wired router and not have to use the wifi itself for these sorts of things.

I would imagine that unless your friend has a domicile with extremely unusual construction there should be a large variety of wi-fi devices capable of reaching between a couple of floors in the home. My Netgear 3700 can actually be connected to almost a block away from my house depending on which direction it is. It can also easily cover both floors and the basement of my 3700 sq ft home. For best range make sure you are using the 2.4ghz band.