I can’t see myself in the network

what am I doing wrong? I installed a wireless router to my main computer, and I can even connect to the internet from that computer. But I can’t see my computer as a part of a group. I am running winXP on all computers. I have installed usb wireless adapters on 2 other computers, but I can’t see them.What am I forgetting to do, so that I can see all computers in the group and start sharing files?