No ip adress, no internet

Hello,
We have had our computer for about 2 years now. We believe it had a virus and crashed... we completely rebooted but could not find out original discs that came with the computer. When we were done rebooting the internet said it was connected but it was not... and it was not reading any ip address even when put in manually. We live in an apartment and all the computers go to one modem. We have tried everything... ipconfig is not working. We are not computer wizzes but we know what we are doing. I can not got on the internet so I can not download any drivers from there... does anyone have any idea what we could do?? please help! we can not afford to buy another computer at the current moment. thank you.