Disabling PCI Ethernet adapters

Hello,
I’ve been advised by my ISP to disable a client’s onboard PCI Daviscom ethernet adapter since the DNS settings are conflicting with his modem. Despite physically removing the card and all settings in device manager (win98,2nd ed.)and disabling the P’n P in the bios, it is still autodetected on start up. Any ideas as to how to solve this? Perhaps reassigning the IRQ? Thanks.