Well if you want to bring up items unrelated to the topic of making linux a successful desktop OS just to make your point then go ahead.
Because they seem unrelated doesn't make it so. People have all sorts of crazy hardware sometimes. Weird SCSI stuff is not uncommon; used to be the only way you could burn a cdrom. Stuff they picked up from work. Lots of people have old Macs and Ibooks and such that are fairly worthless for newer versions of OS X, but will run Linux fine.
Like my ancient Compaq Proliant server. Linux still runs on it, it's still usable in a sort of limited fasion. I realy realy doubt that I'd ever get XP to work on it, or even W2k. I've known people to take home old rs/6000 machines. I've installed Linux on ancient 486 laptops and used them as text terminals for my desktop. It worked very nice and I could launch GUI applications from that terminal to my desktop with simple commands. Like Quake3 and I could control the cdrom and play music from there while in-game.
I've also used older PCs a X terminals for larger PCs and got very good performance for software that otherwise would of never ran on those things.
If your argueing what OS has better hardware support out of the box, then Linux does. For the simple fact that it supports much more hardware out of the box. I know that you probably don't beleive me, but if you can find me a resource were XP has listed out-of-the-box support for various hardware chipsets then I can bring up a comparision for you if you realy realy want one.
Of course XP is going to have very good support out of the box for fairly modern hardware that is typically found in consumer PCs. Microsoft isn't stupid and would go through great lengths to make sure of this.
I can do that too.
Heres one: All OEM's sell their consumer pc's with windows on it, therefore windows is the best OS. (/sarcasm)
Actually for most people this is going to be true. Windows XP doesn't require any extra drivers or user intervention to get working. It's going to be pre-installed, pre-configured and running a tested and supported configuration. If somebody needs help they can call a phone tech place. The phone tech people will be familar with the software and the configuration and be aware of most of the bugs and problems that a typical user is going to run into with windows on that hardware.
It does not require any install to happen. No dealing with partitions. No dealing with install cdroms or driver downloads. And more then likely it will even have Office and such pre-installed if they need it for whatever reason.
If they go down to the Wallmart they can buy software and have about a 90%-95% chance that it will work fairly well on XP for at least the time being. They also probably use Windows at work and probably are familar with it enough off of the bat that they can get their job done.
This doesn't mean that I won't recommend Linux over Windows if they ask my opinion, but it does mean that I am not going to recommend it to them unless I am willing to help them out when they run into problems or at least make them aware of the problems they could run into. With Windows you can get help from lots of different places and even though it's usually expensive it is usually effective. But with Linux they are SOL unless they know somebody that is familar with it.