4 of the 5 computers in the house can connect and browse the internet just fine. The 5th computer is connected to the router, can ping numerous websites and dns servers, can connect via Yahoo messenger and AIM, can download updates from windows update, virus scanner, java, and numerous other pieces of software, but can't browse the internet with either IExplorer or FireFox. Computer is running Vista.

Somehting must have changed on that PC. Was something installed? Downloaded? Setting changed?

To me it sounds like a DNS issue or proxying issue.

1. When you ping websites, do you ping by name or IP? If it's name then you can count out DNS because obviously it's resolving this.

2. Check to see if proxying was set. Since I am assuming you don't have a proxy setup for your home network (just an assumption as to it's very unlikely). Some malware will flip on your proxy causing similar issues. Inside INternet Explorer > Tools> Internet Options > Connections > LAN Settings > Check the box that says automatically detect settings!

Again this is assuming there is no proxy setup on your network. Also, this is just my opinion, I am sure you'll get much more answers following mine, whether it's correcting my post or giving more advice!

Good Luck!

Rick

P.S. Could you do an ipconfig /all in command prompt and display results. I just want to make sure you're receiving legit digits :)

Nothing was changed or installed. I've checked firewalls and ports as well and everything is open.

I'd set the DNS entries manually on the problem computer.

Did you check your proxy settings? I would also set the DNS manually.

I never use automatic settings, and if the dns information wasn't set right not only would I not be able to browse the internet but I wouldn't be able to connect to any of the services listed in the original question.

There is no proxy. I never use automatic settings, and if the dns information wasn't set right not only would I not be able to browse the internet but I wouldn't be able to connect to any of the services listed in the original question.

I know there is no proxy setup on your network but malware among other things can turn this on in your PC. Have you checked to see if your browser was looking for a proxy server?

Have you tried resetting your TCP/IP stack and/or Winsock?

Resetting TCP/IP Stack instructions:
http://support.microsoft.com/default.aspx?scid=kb;en-us;299357

Resetting WINSOCK Instructions:
http://support.microsoft.com/kb/811259/

Hope this helps!

Like I said, no proxy. Haven't tried reseting the stacks or winsock, will try as soon as I get a chance.

Have you tried resetting yout TCP/IP and Winsock?