Something similar seen and the cause seems to be power settings, the laptop occasionally insists on putting the wifi card into hibernation to save battery power even though its usually operating on mains. The laptop concerned is an Acer, which has an Acer utility to configure power setting, I think it may do so in conflict with windows Xp power settings. Once configured it’s normally ok for a few cold starts, but then it goes back to trying to hibernate. When it’s in the hibernated state the usual report is can’t find a network, rather than no wi fi card attached.
Rickity