Bios splash screen then blank

I started my computer (Compaq Presario desktop 2gb ram, 140gb hd, 2.2ghz cpu, win 7 ultimate) a few days ago and it would show the HP splash screen and then go black with a flashing cursor in the upper left corner. I shut it down and restarted and went to setup and reset the defaults and it started. Now every time I start the computer I have to reset the defaults for it to boot.
I couldn't find anything similar to my problem, I looked.
I hope I put this in the right spot.
Thanks.