If you don't have a XP installation media with baseline SATA drivers in it (all the newer OEM ones did) then you can't install XP on a SATA without the BIOS being in ATA mode. Native XP doesn't know about SATA drivers.
It's a bit of a hassle to make a driver slipstreamed disk, but can be done in less than an hour usually, then you can install XP on the system fairly easily and gain the performance enhancements.