SpannerInTheWerks,
I'd looked at downgrading a VAIO to XP but, although Sony Support supply packages to carry out the installation, the end of their instructions states:
Important notes :
• DVD playback is not natively supported in Windows XP, so a separate program is needed in order to playback DVD movies. This software will not be supplied by Sony.
• Instant-on is not available for under Windows XP. This means that the AV button to play music, pictures or DVD’s from within a separate, non XP, environment is not possible.
• In Windows XP only CD burning is natively supported, for DVD burning a separate program is needed. This software will not be supplied by Sony.