[fred cook]

Can you boot it up in a safe mode? If so, from there run a "scandisc" to see if you have bad disc sectors. If so, this will isolate them and (hopefully) let the pc go thru it's boot cycle. If you have a boot disc that came with the pc, use it to get the system up and see what you can find out from there. Could either be a bad motherboard or a hard drive that is going bad. Good luck!