says wireless passcode is incorrect, but it isn't

Hello,

I recently had to reformat my laptop (dell inspiron 1525 with Vista) due to a virus and set it back to the factory settings.  Unfortunately, now I can no longer connect to the wireless internet at my house.  I had no problems before the reformat.  Now when I try to get onto the internet, i can see the wireless connection that I want.  I click it, type in the key code to access the network, but a message appears saying it is the incorrect keycode and it is not.   I called Dell Tech support and after getting transfered around for a while, they informed me that my phone support subscription was expired and I would have to pay. All they could do untill then is give me a hint that I should try deleting a profile.  I went in to manage my networks, but no profiles for any networks appeared.  I went to the tech support at my shcool and they couldn't help me either. PLEASE! Anything that might work! I am getting desperate.