U must check your bios and see in which mode you have set your SATA controller (IDE, AHCI, RAID). In case of AHCI or RAID, u must use when install XP press F6 and provide install floppy with drivers for your hardware. Or set your SATA controller to IDE mode and install XP without problems. But when you change disk to Vista, must set SATA to previous setting. I hope this help :-)