assuming that you will be adding the SATA drive as additional data drive, then simply attach the drive to the motherboard (powered off syempre) and connect the corresponding SATA data/power cables.
be careful with the SATA data cable. don't bend it if possible.
after double checking everything, turn on PC and boot to bios. either via pressing the delete button or either F1 or F2 buttons.
navigate to a menu which shows SATA options and see if you can enable it. depende talaga sa bios and motherboard manufacturer ang options na yan. save settings then exit, then boot to windows xp.
using windows explorer navigate and see if the drive is recognized but no capacity is shown. if the drive is there, then Start > All Programs > control panel > administrative tools > computer management > select storage > disk management. wherein you have to define or partition your drives. NTFS is preferred. the beauty of this is that you partition/format from windows without rebooting. as long as you don't touch your main boot drive and backup your precious data before even installing the SATA drive. then you may proceed with disk management.
summary.
backup your data first.