I still can't connect to the internet! Why?

I have called the ISP and they said to call Microsoft, and Microsoft said to Call HP, and HP said the older systems are obsolete(which my system is from 03). I need help. I can't connect and I have tried just about everything. It recognizes that there is a signal but I can't connect to the internet. Signal is at 100%. I have replaced the NIC, reset the modem, uninstalled the drivers and re-installed, etc. But I think that I there must have been something deleted from the Add/Remove programs list. Is there anything(like a program) that should be in the Add/Remove programs list, that if it was removed it would not allow me to connect to the internet?