Windows 7 64x Network Problems

Hi

Let me explain my problem.

About 2 days ago my brother found my computer on the network. He is using Vista. Now he cant. Ive tried everything:

Ive tried:
-Pinging, network searching
-Update my network drivers
-Uninstalling and reinstalling my network drivers
-Configured my network&sharecenter
-The network does not ask for password
-We are both in the same workgroup
-He has no password protection
-Both has no firewall
-Tried switching workgroup
-Looked up common problems (bonjour), didnt give any results...
-Tried with both firewall and without
-Pulling the cords and inserting them again
-Installed and uninstalled network protokolls (ipv6, lltd and so on, all are active again)
-We both can surf the net as usual
-Tried switching from home network to workplace network

Im thinking it might be our modem... (it has a built in router)

-The pings werent successful. They timed out. I tried typing in the IP and the host name directly, none worked.

-In network & sharing, I disabled homegroup. Ive tried using Home network and workplace network. In advanced settings ive disabled the 120bit encryption, turned off password protection, activated printer sharing. Most of the options have been turned off and on, on both computers.

-My modem is a Xavi 5258, dont know what firmware (honestly i dont know how to look it up), but i know this one isnt good. Im trying to get a new one from my internet provider.

-Current Network Protocols on both computers:
File and Sharing for microsoft networks
Internet protocol version 6
------- "" ------- version 4
Link-layer topology discovery mapper i/o driver
Link-layer topology discovery responder

-Both computers are wired.

-Im using Gigabyte integrated realtek RTL8168C(p) / RTL8111 with the latest driver 7.x (now strangly named "Realtek PCIe GBE Family Controller after driver update)

Im sorry, but i cant provide images at this moment.

This might seem like a stupid question, because you've allready done just about everything, but have you activated the NetBIOS for TCP/IP (properties for local network>properties for TCP/IP>General>Advanced>WINS)?

Both our adapters are set to give us an IP, i havnt put one in manually. Have tried it tho, without luck.

Network discovery is on, on both computers, however my brother vista comp has his status at "costum" and it cant be changed to "active/on"... Ive also tried this for days...

Homegroup i closed, IPv6 has been turned on and off multiple times without avail.

But a strange question... Can networks sometimes take some hours to settle in? I mean make the settings really kick in? Now it all works for some strange reason, with my config as i stated further up. Wich it didnt do yesterday...

Oh well, i dont think that it'll work for long... Thanks for your help so far

Another Windows 7 related issue...

You said you tried deleting the connection from Device Manager (thereby uninstalling it) then restarting? It could be the IP stack need be refreshing.