adapter disappears

I have set up a home network using Microsoft wireless
system. A mn-700 base station on XP and 2 win98se
computers using mn-730 cards. The base staion installed
flawlessly and one computer also. The second computer
installed just fine intially and the network was
operating. But when I shut down the system to venture out
and come back home the second computer can't find the mn-
730 card (the other computers work fine). What do I need
to do for the computer to find the card. Thanks