Hi
You have to explain...
What motherboard and what HDD?
You probably have to load drivers for the SATA controller during XP install.
The driver should be on a floppy - early in the installation process, press F6.
If you don't have a floppy drive you have to make a slipstreamed XP disc with the driver included.
Or - easier, if there's an option in BIOS to set SATA to IDE mode - do that.