Yes, and onboard NICs communicate with the OS in exactly the same way that NIC cards do, they are just on the internal bus rather than the bus that the cards plug into.
This is actually rather easy to determine. I have an antique Pentium II 450 with an onboard Digital ethernet adapter and a PCI NIC with a much newer Digital chipset. The onboard NIC is obviously the same age as the mobo. The PCI NIC is about 6 months old.
OpenBSD shows them as de0 and de1. dmesg shows one on PCI bus 0 and one on PCI bus 1.
I saw that, and asked if it was the same adapter the guy had. If it’s not the same adapter then it means nothing.
Well, maybe so maybe no. If the cards are the same (I don't know, he didn't give enough information) then the point is proven. But even if the cards aren't, the machine is using a industry standard NIC from a major box supplier. The OS should support it, at least in some degraded mode.
It would be different if it was some rare, obscure hardware like a Token Ring card or an ATM card. But it's an Ethernet card. And Ethernet is Ethernet.
Maybe they do maybe they don’t. You can’t make universal statements like that. There’s many manufacturers of motherboards and onboard NICs. Some will follow the generic protocols some won’t. The ones that do follow the generic protocols will work with the generic drivers that ship with XP, the ones that don’t won’t. Another part of the problem is they might not announce themselves properly to XP, there’s a lot of places PnP can fall down, so even if the adapter will work with the generic XP drivers if it doesn’t establish itself with XP as a network adapter that will work with the generic drivers XP won’t try to run it with the generic drivers.
Ethernet might be ethernet, but cards aren’t always cards. If his adapter isn’t 2001 generic, or doesn’t announce through the PnP that it’s 2001 generic then XP won’t work or won’t know it can work. There’s a lot of things missing from the article to determine the exact problem. He could have gone to Device Manager and learned a lot. Anything that shows up in Unknown Devices is not communicating itself to XP properly, thus XP doesn’t know what it is and doesn’t know which generic drivers to try to use with it. You might actually be able to get the generic drivers to work, I’ve done that before, taken a network that was showing as Unknown told Windows it was a network card and it worked long enough to go get the full drivers. He didn’t bother with that though, he just complained about a 2001 OS not living up to 2008 standards and then lied about manufacturers other than Dell not shipping driver disks.