Once you change the BIOS settings to Onboard Video, you need to change where the Monitor cable is plugged in, remove it from the 8400GS and put it onto the Mobo's VGA port at the Back.
Your BSOD has been caused due to a bad video card, namely the 8400GS. it could also be driver corruption but since you updated the drivers and it didn't work, my suggestion would, to remove the 8400GS from within the Box and get a new GPU, until then use the onboard video.
ok i switched to the onboard video and everything seems fine. My dad doesn't really do anything other than email, so can this be a permanent fix or is it wise to do something about the gpu?