why wont my laptop connect to the internet?

monday night i was on the internet just fine. then on tuesday, the computer said no OS. so i reinstalled WinXP. then the computer wouldnt even acknowledge the wireless internet chip. had to take it to the shop where i found out that there were no drivers. so they installed the drivers and said that should work. so i go home and yet still no internet. I am at a loss (and very frustrated). please please can somebody help.