I merged these two topics and moved to Mac Hosts, since the problem is likely on the host, not with the VM.
AndreaGRC wrote:where to download this 'Virtualbox NDIS Bridged Networking Adapter'?
It seems not to be present in the VirtualBox Guest Additions.
The Virtualbox NDIS driver is not in the Guest Additions. It comes with a full installation of Virtualbox and only goes in the host OS, not in the VM. So you won't see it inside XP, only in the Mac, if NDIS drivers go on the Mac OS in the first place. I am not skilled in Mac, so I don't know how Virtualbox Bridged is set up in a Mac.
It is possible to turn off Bridged networking during an installation of Virtualbox. If Bridged is turned off then you wouldn't get the NDIS driver. If you don't have it now, re-install Virtualbox, taking special care with the options, and be sure Bridged is On. Also make sure the host OS is not blocking drivers, you'll need to web-search how to do this or wait for a Mac guru to come in on this topic.
Bridged does not always work over Wi-Fi. See
Virtualbox Networks: In Pictures: Bridged Adapter. Some have reported that setting a static IP address in the VM in the correct IP address range for the Wi-Fi network might get the VM attached through Bridged. Web-search how to set a static IP in XP.
If static IP does not get your XP on the network, you can test with wired Ethernet, and Bridged to the Wired adapter, XP should probably get an IP address through DHCP.
XP is very old and most websites are too advanced for XP to talk to. If you ping Google at 8.8.8.8 and get good responses then XP is connected to the internet. After that, you have to find browsers and software that is compatible with modern internet security protocols.