It sounds like your machine is not recognising the XP installation on your hard disk.
What did you do to add the SATA drive ?
Was it simply an additional disk to store data ?
Have you rebooted since the change and was all ok ?
Have a look at your BIOS and check the boot order
Try removing the SATA disk and boot (unplug the cables)
What program did you install ?
Can you get into Safemode or do you not even get the option ?