Flashing line, computer will not boot.?

My computer will not fully start up because it always gets stuck on a flashing white line on the top left corner. I have been having issues with my video card recently (ati radeon 4850) where a red light will go on and my monitor will go black therefore making me have to hard reboot my computer. I do not know what this red light means so if someone could help me that we would be awesome as well. This line I was stuck on happened after one of the red light issues so I hard rebooted and that's where I'm stuck now. I am trying to reformat now and it is telling me that no device drivers were found and make sure the installation media contains the right drivers, which makes no sense to me because that has never happened to me. Please help.