I did a fresh install of VirtualBox on my Mac Book Pro and then install Windows XP. Once installed I noticed that there was no network card showing up under “Network Connections”. I checked out the Device Manager and found that the network card was showing up with now driver. After searching around, I figured out that the AMD PCNET III driver seems to work out of the box. If you power down the machine and change the adapter, it should detect and install properly and you’re good to go.