If you need step-by-step instructions, I can post this later tonight. Essentually, you do ther following (this is from rote memory - I will check this later for accuracy);
1. Disconect the USB cable.
2. If you are on broadband, make sure that the modem is connected to cable.
3. Connect the CAT-5 cable from the ethernet card on the machine to an ampty ethernet port on the modem.
4. In Mandriva, go to start-->system-->configuration-->configure my computer. Pick Network connection/setup.
5. Follow the wizard. It should detect your ethernet card. Choose auto DHCP and follow the prompts. If you have dynamic DHCP from your provider, ignore DNS settings and such and just hit enter to toggle through the menu prompts. Tell Mandriva to connect on boot and complete the setup.
6. The network wizard should restart the network services and you can test the internet connection with Konqueror, or whatever browser that you are using.
7. If it does not work right away, re-boot and see if you get an internet connection.
If you have DSL, it gets a little more complicated. Let us know if you have DSL and need to login to your provider.
On newer systems, Mandriva may not detect your nForce card right off, but Mandriva is pretty good about this support.
Let us know if it works. If not, let us know what motherboard or system that you have, and if possible, what ethernet card is in the system. if in doubt, consult your users manual.