for checksum error, you should replace the mobo battery. locate the coin type battery on you mobo. It will be a CR2032 and you'd find one in most computer repair shops or watch repair shops.
but the fact that it keeps restarting is not related to the checksum error. So am i understanding this correct? your pc gets in a reboot loop? you start it, it shows checksum error, you load defaults and then it does not go into windows and instead reboots?