Restart your computer repeatedly tapping the f8 key to enter safe mode while the screen is black once in safe mode where the only things working will be your keyboard and mouse allowing you to attempt to repair your computer

you could select the option start at last known configuration that worked this will tell you if and what file has been corrupted or missing then you will know if its a hardware issue then select restart if the problem still persists f8 back into safe mode you might need to select your operating system to load into safe mode

click start control panel administration tools computer management in the left panel events + to expand then system you will see all errors in right panel right click select properties this will tell you what has occurred and the time it occurred

you might use the system restore to restore your system to an earlier time click start all programs accessories system tools you should see your system restore option if it is a hardware issue the system restore might not work

hope this helps you