|I am guessing you have Vista installed when using AHCI settings? If that is the case you can't change it to IDE compatibility mode and expect it to boot.|
What you need to do is to slipstream the motherboard required SATA controller drivers into your WinXP files. Then burn a new CDR and use it to install WinXP.
This is necessary because WinXP can't natively configure SATA hard drives.
Even if you do that you may run into trouble because the computer may balk at installing an older OS than the one currently installed.
Another issue might be finding the necessary hardware drivers for WinXP, including the SATA drivers.
I suggest you just forget the whole idea. What is the reason you want to run WinXP?