if you have another pc make a http://www.hiren.info/pages/bootcd
and boot from it. try some of the disk tools. it may be that the mbr is damaged and can be fixed. if the drive is fine but needs the system restore to run..hirum has a mini xp boot you should be able to boot from it and copy your work over to a usb stick or ext hard drive. one thing to check see if your son changed anything in the bios. i would go in and set it to factory default and re boot and see if the hard drive boots.