A network problem I have not seen before ...

[QuietDad]

You can also eliminate the router by plugging the PC directly to the modem. If that works, then the issue is in the router and a whole different direction to take it.

 

[QuietDad]

The next thing I would do/look for is see if I have HOSTS file (c:\windows\system32\drivers\ect\HOSTS) that has some weird entry (renaming it to HOST.OLD or something and trying) then plugging the PC directly into the modem with dynamic IP set just to totally rule out the router.
Have you tried booting the PC in safe mode with networking?

 

[Rudy Toody]

This sounds like a firewall issue. You can stealth your computer so nobody can see any ports and the way the firewall handles that, is to restrict incomming port 80 to messages that were prompted by an internal process (the browser). Somehow, that trigger is not working. Probably, something in the registry.

Snoop around with this to get ideas: https://www.grc.com/ShieldsUp!

 

[petrusbroder]

Yes, this is puzzling.

• I have tried a different port on the router - does not matter.
• I have installed a WiFi-USB modem - the problem remains.
• All other computers can see the shared files folder and the contents.
• No, I do not use any customized settings (to lazy for that ...)

I think that this is a problem specific for browsing because:

• I can ping any IP-addy or any http-addy on my LAN and on the internet.
• I can trace any IP- or http-addy on the internet.
• I can see all the computers on the LAN.
• The other computers can see the affected computer.
• I can see all the "shared files"-folders and their contenst on the other computers on the LAN.
• I can share media files between computers using the MS Media Player and collect media from other computers using iTunes.
• I can remotely connect to the affected computer using a other computer on the LAN.

What is this probably not?

• firewall (it is uninstalled and gone)
• AVP or anti-malware software (I don't have any)
• ARP-cache and DNS-cache (flushed them many times).
• hardware (NIC or WiFi, have changed those, installed new drivers, etc)
• router (all other comps work ok irrespective of port#)
• switch (haver disconnected that one ...)
• IPv6 (is disabled)
• ISP (they have checked and see all the traffic from my other computers) and from the affected computer when ping-ing or tracing)
• Probably not a malware/virus, (I have let a lap top scan all the HDD - taken them out from the affected computer, connected to an "older" laptop with only OS and four different AVPs and three different anti-malware progs using a USB-SATA converter)

Thus the problems are:

1. browsing the 'net using Firefox, IE or Chrome ( I have no other browsers)
2. getting BOINC to connect to the 'net.

Interesting ... isnt it?

Well, reformatting and a new system install seems the only way to get the computer connected. And yes, I have invested a lot of time into this problem, and I think I have done it systematically. Why? Not only to solve a problem, although that gives a lot of satisfaction when successful, but mainly to learn more. Thanks for all of you helping out and inspiring me to learn more.

This is what I really like about the net in general and the Anandtech forums in particular. Oh BTW, I have not yet learned to fly ... (see my sig ...)

 

[VirtualLarry]

http://www.tweaking.com/content/page/windows_repair_all_in_one.html

Could try this fix-it program.

 

[petrusbroder]

Thanks for the suggestion, VirualLarry. It did not help ...

 

[VirtualLarry]

Have you tried a full restart? Shut all of your PCs down, shut down your networking equipment, shut down the modem, and then bring it all back up again?

I know that you have a lot of equipment, but this is a basic network troubleshooting step.

I'm starting to believe that the problem lies in some networking gear and not your PC.

Of course, if you re-format, and it's still not fixed, then you will know this to be true.

 

[AnonymouseUser]

If you haven't already reinstalled Windows, boot to a light Linux LiveUSB (eg, Xubuntu) and see if it can connect. If it connects with Linux you have a Windows/software/driver issue. If it doesn't connect then it's either a hardware issue or another device in the network.

 

[mcveigh]

If you haven't already reinstalled Windows, boot to a light Linux LiveUSB (eg, Xubuntu) and see if it can connect. If it connects with Linux you have a Windows/software/driver issue. If it doesn't connect then it's either a hardware issue or another device in the network.

That's what I was coming in to suggest.
I really hope something works and OP reports back!