So far nobody posted any experiences about XP on the Pi 3540.
To install XP you will first have to integrate a driver for your S-ATA-controller into your XP-CD following this how-to:
http://www.amilo-forum.com/topic,26,-Installation-of-Windows-XP-Home-Pro-PE-FAQs.htmlThen you will have to find the drivers for all the components (chipset, graphics, ethernet...). This will be easier if you read out your hardware on your current Vista-installation.
You can use
Everest to do so. Please attach a report in HTML/XML-format if you need any help to find the drivers.