Sata Conflict

It is really bizarre. Sometimes I come back to my computer and Vista boots right up from hibernation. Other times when I come back its already booted up in xp. I put Vista on my raptor drive and have xp on the barracuda drive. They are both sata. Is there some setting I have to make in the bios so this stops? Whenever I come back to xp being loaded my raptor drive is not present anymore. Is this a sata channel conflict or is my abit board causing a sata confliction.