Do you have any bootable cds? such as a real Windows OS install cd or a linux cd, or even a memtest cd?
What I'm getting at is: If the computer will boot off a cd, then you know the drive isn't dead, so therefore its a software issue, and sometimes this can be resolved by deleting the drive in device manager and rebooting. If the computer won't boot off the cd either your BIOS isn't set to look to boot off a cd (which is changeable) or the drive is dead.