Can't get belking router and blkn dsktp card to work together

[jca2007]

I have windows xp media center, and I bought a Belkin Wireless G Desktop Card and Router, for my new comp and my old comp, I can not what so ever get the old comp with the Wireless pci card to pick up my router on my new computer, I have copied the encryption key that microsoft had made for me, and the program that came with the disk, but neither one is not working. What should I do?