Help Disk Boot Failure XP

HI
If possible can someone help me
recently my sony cdrw/dvd rom died on me i replaced it with a Pioneer DVR-112,
i removed the old drive, plugged in the new
stared the computer, it took a while to load up, but it did load up and everything seem to be running fine, a few hours later the compuetre crashed, restarted and came up with the message disk boot failure insert legacy disk
looking on the bios boot tab the ide hard drive was 2nd on the boot list and was displaying that there was no HD
i do not have the greatest understanding of the mechanics of computers so any hlp would be apprecited
thanks
chris