Network From Hell

Can someone set me straight? Three computers "A" and "B" are desktops. "C" is a laptop.
All OS's are Win 7 SP 1.

I can get a network installed on "B" and "C" which lets me talk between "B" and "C". When I try to install a network on "A" all it lets me do is establish a net connection. I have beat my head against a wall for two days now. Any guidance?

Mine is set to automatically obtain as you show.

"C" is a laptop ----- No problem has a working network

"A" is a desktop --- Can't get working network

"B" is a desktop -- No problem has a working network

How did you join the networks? Did you try using windows 7 homegroups? Do you have any special firewall or vpn software on the laptop?

Are A and B connected wired to the router and laptop is wireless? (Just want to confirm)

Also please post an ipconfig\all on the laptop.

"B" and "C" are connected via wireless (networks operating).

"A" is connected via cat 5 ethernet . "A" is one not working.

Using Win 7 to form a home group. Can only get a net connection. Can't see other two computers.

Firewall ---- Norton Internet security

Tried turn Norton firewall off. Tried with Win 7 firewall. Tried NO firewalls.

Can A ping the router?

replace ethernet cable if not.

Can A get a valid ip?

Try resetting router to factory defaults.

Ping works. I think I have found the problem. When I look at the detected computers in Explorer (the tree) sometimes I can see the computer and sometimes I can't. That tells me I am losing discovery of the machine as it comes and goes.

What I have done is order a TP-LINK Archer T4U AC1200 Wireless Dual Band USB 3.0 Adapter.

I'll convert the machine to a wireless sig and that may cure the problem.

OK I got it. I guess the wireless adapter I talked about buying was a needless purchase. Maybe I'll use it anyhow.

There was multiple problems:

Had to set a value in the registry to permit a signal from a computer on the same net work.

Hkey_Local_Machine\System\CurrentControlSet\services\Tcpip\Parameters

IPEnableRouter = data value should have been 1. set to 1 from 0. Networks have worked before on this machine and I never ever changed it. Maybe the router I was using didn't care. Or the gremlins changed it. This problem was only on one machine, the others were OK.

Two of the machines is running Norton Internet Suite. I have never had any problem with this software. I turned the firewall off and rebooted on both machines multiple times. It appeared that it had no effect. Alas appearances are not what they alway seem. In the Norton firewall there is a section called trust center. The machines that are going to be in the net have to be entered with a mac and a name, etc. Then they need to be granted full trust or some measure thereof. I went full trust. I had to do that on the two desktops. I would imagine the results from these settings cause some rules to be written to the fire wall.

Then there was some other tweaks that I applied that I really don't know what effect they had because they didn't show any progress.

All three machines can now talk to anyone of the other two. Thank you for your reply.