Network issues with XP and Win7

Heya, I have a problem which I was hoping you guys could help me out with. I have looked around but can't find anything related to my problem. (Not the easiest thing to search for either.)

Anyway the problem is this (short version first, details after):
A single computer connected through a broadband connection with static IP was working fine, first in xp and then after some driver issues also in win 7 (64). However when I tried to connect a different computer it suddenly doesn't work .. on either computer, despite having changed nothing. It does however work just fine on this notebook which is running XP.

Atm I'm stuck with this notebook and can't get either win 7 computer going again.

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I'm at a location with a static ip connection, connected directly to the modem itself which is locked to the ISP specs by a password.

There's normally only one computer connected here and it was running win 7 just fine. I did have similar issues when installing win7 though, it was using a realtek card and the solution was to use older vista drivers to make it work.

My home computer which I wanted to use instead of the regular one is running fine and works great with my NAT address at home.

The XP laptop is an older model and it works just fine with either connection.

Now for some specifics:
I cannot ping my gateway on either computer running win7 and if I run a diagnostic it says that "the computer seems to be correctly configured but the dns doesn't seem to be working".
I've tried pinging an ipaddress directly as well as surfing to it but so far no luck.
I can ping my own IP on both computers so it's not the cards.
Both machines are also running double network cards where only one is in use and no connection sharing.

I have tried resetting the modem, restarting, flushing the dns, reset winsock, uninstalling the drivers on the original computer, removing the homegroup, creating a new connection, disabling automatic network discovery (and enabling again ofc) but so far nothing works.

I am using comodo firewall on all three computers and also tried uninstalling it on one of them.

I have also disabled the windows firewall completely.

The only thing I'm slightly unsure about is the net mask for the connection but seeing as it's working here I'm guessing it's the standard 255.255.255.0.


I have no idea what else to try and would be greatful for any help or suggestion on what to do next.

What weirds me out the most is the fact that all I did to begin with was connect the cable to a different computer and then when I connected to the original computer again nothing is working :P

I also forgot to mention that I have tested with a different cable.

I should also add that all cards I have tried with except for the Laptop (which works) are realtek cardsso it might be a realtek issue I guess.
2 onboard and 2 standalone.

No ideas at all then? I have now tried everything I can think of and all the suggestions found through google multiple times without success. I tried using another modem in case that was messing it up but nope. I've tried to reinstall the drivers, reset all related services I could find ... everything and then some. It doesn't work on either of the win 7 machines but it works just fine on this old XP laptop. I even tried to use wireshark to sniff the traffic and from what my limited knowledge can decipher it seems that the ARP requests as well as some IGMP requests make it to the gateway and back but nothing else. Still thankful for any ideas you can think of. /edit for some reason it's not saving the formatting for this post so just bare with me :P

Computer Not Showing In Network.
Need Help I Have 2 Machine One XP Another Win7 With Switch.
XP Workgroup (Workgroup)
192.168.1.10
255.255.255.0
widows 7 Workgroup (Workgroup)
192.168.1.2
255.255.255.0