Can your computer communicate with the others on your home network? Try linking the down computer with the laptop and connect to the net through through an ad hoc setup in your network. It'll give clues to the nature of your problem.
hmmm... you sure it's not a virus? I used to have this "spyware" called newnet (or something)... basically they are a "company" which sell certain domain names which don't actually exist in the way one would usually assume they would. They only work if all browser requests go through their software. However, if this has previously been removed then you might have a problem as the browser is still looking for the software (which has been removed). Try Spybot Search and Destroy, untick all options (as by default some might be overlooked by the programme). This might not be the problem, but worth a try. You said you looked for viruses, but did you look for spyware? Try CWShredder, AdAware, and Spybot.
To check/change your TCP/IP settings: Since you didn't indicate your OS, we'll use Win2000: Start -> Settings -> Control Panel -> Network & Dial-up connections or On desktop, right-click on 'My Network Places' -> Properties Then right-click on 'local area connection' -> Properties click on 'Internet Protocol (TCP/IP' - > Properties -> Advanced You will now see four tabs (IP SEttings, DNS, WINS, and Options). Adjust these settings to be identical to the ones on your notebook. If you use WinXP, you will get to the TCP/IP settings in a similar way to what's listed above - just fumble around with it.
Try a different NIC then. Surely you have another one sitting around the house somewhere. Have you tried reinstalling your NIC driver as well? Remove it from device manager and reboot and let it redetect. Also what is the IP you're getting? is it 169.xxx.xxx.xxx or is it 0.0.0.0? Try removing all protocols from your NIC properties except for TCP/IP. Get rid of IPX and and anything else for now for troubleshooting purposes.
Do you have Windows XP? If so... WinSock XP Fix If that doesn't work, try deleting your network drivers, restarting, and letting them re-install themselves. EDIT: And like Ace said, make sure it's not spyware or a virus that's affecting your connection. Take a glance through your programs list...I know New.net and 180searchassistant in particular can mess with your network config... Windows 2000 seems especially vulnerable to 180searchassistant, for no apparent reason. And of course run Spybot, Adaware, all that junk.
UPDATE: turns out it was Norton Internet Security causing all the problems. Once i disabled it, my internet worked fine. I have no idea why after a year of working flawlessly it decided to do this, but atleast I can get the internet now.
Wow, I don't know why I didn't think of that. That's one of the first things I check on every broke internet case. Norton Internet Security and McAfee Security Center suck. They screw with your connection so bad. Norton AntiVirus and McAfee VirusScan are great though...
I had something like this happen to me. For no reason, Internet connection disappeared. I remembered I had ZoneLabs ZoneAlarm and it was blocking internet access, and I uninstalled it after I added XP's SP2... that put an additional firewall, and the whole think went kaput. After a series of calling Yahoo and getting the lady to reconfigure my shiznit, we came to the conclusion that the problem was on my machine, not a virus, not an AD program, not their software. It was that XP remembered that ZONEAlarm had a setting still running on my machine and blocking stuff out. I could connect Yahoo Instant Messenger for a while, talk on MSN Messenger for a while, and then it would disconnect. I stated that my stuff was reconfigured and even then it didn't change connection to the YAHOO Instant Messenger or AOL IM or MSN IM. After that, I started going through the services and found some "Vector" network service from ZoneAlarm still on my machine that I didn't remove referenced some DLL stuff on my system folder. I had to boot the machine in SAFE MODE under DOS and remove that shiznit. Dude, see if your firewall is NOT allowing the connection. Check the laptop and compare with the PC to see if the PC has updates that the laptop hasn't gotten, and there is a special patch from Microsoft that says that computers with connection trouble will require it. I believe it's called the "loop" patch... find it at http://support.microsoft.com/ . I will report back if I find it.
