Airport Express and windows 7

Hello,

I have a macbook and a airport express.
I use it mainly for airtunes.
Now I recently bought a windows 7 computer and would love to stream music via this computer. The problem is it doesn't have a wireless network option only ethernet, and I need to use that for my internet cable.
The airport is connected with the same network as the windows 7 computer, but than via wireless connection.

When I look in the Airport-configuration program for the airport it doesn't find it, but I can find it by typing in the IP adress at the option "configure other basestation". When I want to configure it, I lose connection with the AE.

Is it possible to get a fixed and stable connection between the computer and AE?
if so, how?

For more information, feel free to ask me.

thanks for ur time

Looee