XP doesn't support SATA chipsets so you run into brick walls like this. Hopefully you have your current backup so you won't lose it all.
I had functioning computer with a RAID1 array & Win XP Pro SP2. I've upgraded the motherboard, RAM, graphics card & CPU today & I'm pretty sure I have set the BIOS parameters correctly but I can't boot from my old hard disks (SATA). I now suppose it must be a lack of the correct RAID controller but how can I fix that without erasing & reinstalling Windows afresh (which I can't do - all my stuff is on the 2 RAID disks)? Is it not possible to upgrade if one uses RAID? That seems a bit extreme.