Do you have the XP service packs installed ?

Is the drive new ? is it in with the old drive ? is it on a separate IDE channel other than the HD ? make sure the master/slave jumpers a correct. Make sure the IDE cable is good and seated all the way.

Go back into device manager and under IDE ATA /ATAPI controllers un-install the IDE channel that the drive is on. Reboot and let XP install the driver again.