Network configurations

I have a stand-alone desktop running XP connected to the Internet via a
wireless PCI card and microwave link. I would like to add 2 or 3 other
computers to form an 802.11 wireless network. How do I configure this and
what hardware is required. In this case I can't input the Internet
[ethernet] connection into, say, a wireless router - it is fixed into the
first PC. Any assistance greatly appreciated
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Alan M
Sydney - Australia