HELP - computer and modem won't talk!

[Sirius]

Hi - I have been having ongoing problems with internet connection in W7!
All of a sudden my connection dropped again about a month ago... and I have tried everything to get it back up. (pinging the ethernet, network card driver updates, new modem, etc.)

Does anyone have any clue why this might be happening?

When I check my network card in device manager - it says it is fine. I have uninstalled and reinstalled it.

The Networking control panel when doing a trouble shoot tells me I have an Invalid IP address - so I have done the ipconfig release/reset trick too.

I have a Windows XP notebook that connects to the internet fine... so it isnt a prob with the ISP. They told me it might be a problem with the modem - so I bought a new one (Belkin latest model)

I am about to give up on ethernet on this machine and go on Wireless through a USB stick - but I really want to know why on earth this problem keeps happening and if there is a diagnostic I can use to find out what the problem is.
Any suggestions would be greatly appreciated!!
cheers

 

[mckillwashere]

Are you behind a router?

 

[Sirius]

I have a modem/router in one (a new Belkin and a d-link 504T)

 

[mckillwashere]

How are they connected and which one are you actively using?

 

[Sirius]

I would connect through ethernet NIC (Realtek ethernet card) - but I am not connected through anything at the moment because nothing works

 

[mckillwashere]

so you are hard wired to the modem?

Say everything was plugged up the way you want it.
what are the steps a signal would come from the outside to your machine

 

[Sirius]

Signal comes through phone line ADSL connection.
It has worked intermittently ever since I got my W7 machine.
First time we thought it may have been due to a thunder storm zapping the ethernet port so I got a new NIC. Then it worked fine for months.
Then it stopped again - so I unplugged everything and drained the power from the machine.. and it worked again fine for a few months.
Then one night I let an iTunes update download and it never worked again... I tried all the things one would to try and fix it - but nope... no go.

I am starting to wonder if there could be a problem with the motherboard?

I really just want to know what on earth the problem actually is because I can't work it out.