More than likely, if you're running DSL/ADSL, it's a PPPoE connection. This requires authentication in the form of username/password/email or something along those lines.
Unless your M$ setup is configured for PPPoE login, I'm presuming that info is configured in the hardware router (Netgear).
Previously I had a Westell DSL modem that I first had to set to "bridge" modem, to disable NAT, and then I could connect it to the "red" interface on the IPCop machine, at which point I could configure IPCop to use PPPoE on that interface.
I'm on the other side of the pond, so I'm not completely familiar with the configuration of ADSL devices in Europe, but the specs on your DSL modem appear to indicate you can set it to bridge mode: http://www.netgear.com/Products/Rout...Specifications
If you have an IPCop machine up and running, and it's connected to an actual keyboard and monitor, you can log into the console in text mode with the root username/password, then run "setup" to get to the networking configuration, at which point you can select to use PPPoE for the Red interface.
If you've not yet configured anything on your IPCop box, you might want to re-install with the latest version (1.4.18, as of the time of this writing).
Hope this helps. Please let us know how it goes!