You can get OEM disks/machines online. XP is used by around 90% of the planet and by an even higher margin within business. XP is the best supported OS available and SP3 is due sometime soon.

Not really out of date,supported to 2014 at least. You should not choose an OS because it's the "latest" but on its ability to reliably do the things you need to do.
There is nothing you can do in Vista that you can't do in XP.
I do use both.

While some are happy with Vista there are many with problems.

I would have no hesitation in buying XP.

Bob