Now that you have everything backed up (first priority), you can check the hard drive.http://www.hitachigst.com/hdd/support/download.htm#DFT
Download either floppy or CD version (.iso file for CD), put it on proper media, floppy...reboot, change boot order so that floppy is first.
You have to use an iso-burning program if you download the .iso file...to create a bootable CD.
Active@ ISO Burner. Data CD DVD burning software. Write ISO image to CD,DVD,CD-RW,CDR,DVD-RW. - http://www.ntfs.com/iso-burning.htm
If the diagnostic (long test if there is a short and a long available) gives it a clean bill of health, all is well.