Some of the major OEM's offer XP cd's for certain models of their computers that came with Vista. If they are available for your model, there will probably be some cost involved. I have seen this cost be as low as pay for shipping, or as much as $70. You contact toshiba and see what they say.
Otherwise getting XP on some newer laptops can take some digging, as the OEM may not offer XP drivers for that model and you have to source out the drivers from the individual device makers, as in the video or sata drivers.