PC settings problem?

I have a problem, this morning i booted up my pc, to find the screen resolution had changed itself to the lowest settings, i looked on the taskbar and my graphics driver tray app wasn't running, so i went to control panel and changed the resolution back to full. Aftr that it said the screen could not display the screen resolution and to change it to another resolution, which i couldn't do because the pc wouldn't let me do anything after that screen. So i reset the computer in hope it would change the settings back but it came up with the same screen. I tried booting it up in safe mode and it still came up. I also tried waiting and various other things but still no results. Any ideas what to do? im stuck at the moment, Thanks.