It appears like the hard drive is having problems.. Either dead entirely or the connections themselves aren't making contact..

If you've got XP on the drive, was this system working before and it's now stopped functioning? Did you bring the hard drive from another computer without installing the operating system and motherboard drivers after it was connected to the new machine? (XP needs to be installed on the drive AFTER the HD has been connected to the motherboard.)

A little more information would be helpful.