XP acer wifi problem

ok i got my acer like 2 weeks ago.
i went to my friends house and loaded XP on it, and i was able to get on to his wireless network
yesterday me and my friend went to starbucks to figure out how to get on to there wireless
internet and it said that "no wireless networks were found in range". so i checked to see if there was
any wireless signal from my phone, at&t tilt, and there was. then we went to my other friends house to
maybe download new updates or something, and he has wireless in his house and i put my acer right next to it
and again it said "no wireless networks were found in range". we were like wtf!
we plugged in the ethernet cable and it worked, we downloaded what we thought was the new update...which we figured out
later was 270 which was the newest. then we went back to my house and got network stumbler, and then we went back to starbucks to see
if it could pick up any signal or if i had completely dead wifi card. we started net stumbler and it picked up
all kinds of signal, but again we tried to refresh the stupid XP wireless network thing and
it said "no wireless networks were found in range".

plz help!

i know i wrote a lot, and i hope it makes any sense

if anybody has had this problem and fixed it plz help!