I have a desktop computer with a non-Mac OS (it currently runs Windows XP Home Edition, but I'm about to replace/add Ubuntu) which I can't connect to my home network (again, the router is not a Mac product): I don't have an ethernet cable where it currently is and it doesn't have a wireless connection option. I do however have an Airport Express and I wanted to know if it was possible to use it as an "antennae" to set a wireless connection to my network.
I mean, the idea would be something like this:
PC <--(ethernet)--> Airport express <--(wireless)--> Router
EDIT: It CAN be done. I was not allowed to touch a lot of things in the router/network, but I managed to configure the Airport without changing things in the current network. I had to set the IP manually but it is currently working.