This cannot be the first time a kid learned to do this. When you reboot a PC you have a very brief opportunity before Windows loads to hit the F2 key and go into your BIOS settings. One of the settings there is the system clock time. My son reached his time limit and simply rebooted. He went into the BIOS which loads before Windows and rolled the system time back about 3 hours. Then he allowed the computer to continue booting into Windows 7. Windows took the time from the system and allowed him 3 more hours. Of course I recieved a message that stated the clock time was wrong on his computer and he caught Heck for it. But he is the kind of kid that will do it again. How do I prevent tampering with the BIOS or booting into Safe Mode?