If the MBR was corrupted, when you ran the repair disk it should have automatically fixed it (At least mine did). I did not even have to run the repair. As soon as I booted to the Repair disk (or installation disk for that matter) it found the MBR problem and fixed it without running repair.
The Repair Install may be your only option at this point. (your son must be some PC guru to have been able to do this)
When you finally get back online, look into Imaging. With an Up To Date image you can restore a PC that will not boot in about 10 minutes. I create a new Image monthly (at the most) more often if many changes have taken place. I also keep my data on a separate partition so a OS not booting will not affect the data at all. Check the many discussions in the Security and Backup forum. You can search for Imaging or Image software, etc.
Is there any chance with the overclocking you do, something in the hardware may have given up?