Internet Connection

I have a Dell Insperion 530s micro tower that no longer connects to the internet. A few days ago none of the connected devices (2 computers and direct tv box wired, or any wireless device) would connect to the internet. I took the router out of the mix all together and plugged in my computer to the modem directly, in which after some resetting and restarting I was able to get it to connect to the internet. I tryed the other computer and it connected straight away, so i gathered that the router had went bad. Then one morning I was on line with my computer with no problems connecting, and 24 hours later that same computer would not connect to the internet. I have reset the modem, did a restore point to a time when I knew it was connecting fine, uninstalled the NIC and rebooted the computer, did a ip renew and release, let windows vista attempt to fix the problem, and still I cannot get this computer to connect to the internet. The other computer connects just fine each and everytime. I am at a loss as to the reason for this, could someone give me some ideas to try and get this Dell working online again. This one is the one I use for everything, all my saved sites with passwords, the whole thing, the other computer is used by someone else in the house.:(

Thank you in advance for your help!! :)