KDE InfoCenter should list pci devices to show what chip/module is needed for your nic. If not you,as root, should use lspci from terminal to see how nic is described. The chip the nic uses is what counts. Then you,as root again, can run lsmod to see if the needed module is loaded. If not then modprobe module-name may be needed.
You can also get the info from XP device manager or system info applet. Or a kanotix or mepis live-cd's hardware detction can help.
The Mandriva equivalent of Mandrake Control Center or DrakX may offer you easy place to install and configure that nic and get your internet/network setup. And the Mandriva Starter Guide if still available is indispensible for troubleshooting your setup. I still have and find my 8.1 and 9.2 manuals useful for general linux troubleshooting. Welcome to LQ and ask again if you need help