|These are probably out...|
1- Faulty Ram
2- Faulty MOB
3- Faulty HD.
Because he was able to boot to safe mode. 4. Could be the problem but there could be a 5th problem which is a bad driver.
Have you recently installed something on your computer? When you boot to safe mode it does not load all the drivers so you have the chance to remove a faulty driver. You may want to uninstall anything you just recently installed.
Also do a virus scan for option 4.