Cant connect to internet

Hello,

i have 3 laptops. 2 of them r dell inspiron 9100, dell inspiron 1520 and a mac. recently my dell 9100' HD died. I replaced the hard drive w/a new one, installed all necessary software, but i cant get on internet. I have no problem getting online with the other w laptops. going into the WF properties, i see that my gateway # is not there. i go through DOS, ipconfigure,etc. & i get a message that the adapter is not permissible.....pls, anyone any answer.

thnks