Windows 7 IP recognition

Hi,

I have a Windows 7 machine that can no longer recognize the ip, for internet access.
Diagnose problem does not fix it, it simply says can not recognize ip. It says it can
see the network, but the problem is identifying the network.

I believe this problem occurred after a null modem was used on it. But my friend
also said he was downloading something when a bunch of ads popped up and audio.

I cleaned the computer, ran it in safe mode removed all viruses (48) and other little stuff.
Also, reset modem, unplugged, disabled network card, re-enabled, etc:
Still can not connect. IP and DHCP is all set up on automatic. Ran out of ideas =\
please help if possible, thanks in advanced.